Objective To investigate the effects of atropine eye drops of different concentrations and administration frequencies on pupil diameter, accommodative amplitude, and tear film function in myopic children. Methods The left eye data of 280 myopic children who were treated in our hospital from Jan. 2018 to Jan. 2021 were selected. The randomized envelope method was used to divide the patients into 4 groups (groups A, B, C, and D), with 70 cases (70 eyes) in each group. Patients in the group A were given 0.01 % atropine eye drops every night at bedtime (both eyes); patients in the group B were given 0.01 % atropine eye drops every other night at bedtime (both eyes); patients in the group C were given 0.02 % atropine eye drops every night at bedtime (both eyes); patients in the group D were given 0.02 % atropine eye drops every other night at bedtime (both eyes); and all of them were given 1 drop each time per eye. The pupil diameter, accommodative amplitude, equivalent spherical diopter, axial length, anterior chamber depth, tear film function, and adverse reactions of the 4 groups of patients were compared before and 4, 8, and 12 months after treatment. Results Before treatment, there were no significant differences in pupil diameter, accommodative amplitude, equivalent spherical diopter, axial length, anterior chamber depth, or tear film lipid layer thickness between the 4 groups (all P>0.05). There were no significant differences in pupil diameter, accommodative amplitude, equivalent spherical diopter, axial length, anterior chamber depth, or lipid layer thickness before and after treatment between the 4 groups (all P_group>0.05). The change trends of pupil diameter, accommodative amplitude, equivalent spherical diopter, axial length, anterior chamber depth and tear film lipid layer thickness at different time points before and after treatment were the same in each group (all P_time>0.05). At each time point after administration, the pupil diameter and equivalent spherical diopter were significantly greater than those before administration, and the accommodative amplitude was significantly less than that before administration (all P<0.01). At 4 and 8 months after administration there was no significant difference in the axial length of each group compared with that before administration (all P>0.05), but at 12 months after administration the axial length of each group was significantly greater than that before administration (all P<0.05); and there were no significant differences in anterior chamber depth or tear film lipid layer thickness before and after administration in each group (all P>0.05). There were no significant differences in pupil diameter, accommodative amplitude, equivalent spherical diopter, axial length, anterior chamber depth, or tear film lipid layer thickness at each time point between the groups (all P>0.05), and there was no interaction between different treatments and administration time points (all P_interaction>0.05). Within 1 month after treatment, some children were afraid of strong light; according to intention to treat analysis (ITT), there were 12 (17.14 %) cases in the group A, 11 (15.71 %) in the group B, 16 (22.86 %) in the group C, and 13 (18.57 %) in the group D, with no significant difference (P>0.05); according to per-protocol analysis (PP), there were 12 (18.18 %) cases in the group A, 10 (15.62 %) in the group B, 14 (20.90 %) in the group C, and 11 (16.42 %) in the group D, with no significant difference (P>0.05). There were also some myopic children with blur of close-up reading within 1 month after treatment; according to ITT, there were 7 (10.00 %) cases in the group A, 4 (5.71 %) in the group B, 6 (8.57 %) in the group C, and 8 (11.43 %) in the group D, with no significant difference (P>0.05); according to PP, there were 5 (7.58 %) cases in the group A, 3 (4.69 %) in the group B, 6 (8.96 %) in the group C, and 5 (7.46 %) in the group D, with no significant difference (P>0.05). Conclusion Daily or every other day eye drops of 0.01 % or 0.02 % atropine have the same effects on pupil diameter, accommodative amplitude and equivalent spherical diopter of myopic children, and there was no significant difference in adverse reactions.