Objective To investigate the changes of functional connectivity of prefrontal cortex in healthy undergraduates after repeated transcranial direct current stimulation (tDCS).Methods Thirty-nine undergraduates were selected and divided into stimulation group (n＝21) and control group (n＝18) by random number table. tDCS with intensity of 1.5 mA was used to implement 12 interventions for 4 weeks in the stimulation group, and each intervention lasted for 20 min; and the control group was stimulated in the same way by sham tDCS. Functional near infrared spectroscopy (fNIRS) was used to measure the resting prefrontal functional connectivity of pre-test (baseline), in-test (the 14^th day) and post-test (the 28^th day).Results fNIRS data indicated that the proportion of channels with functional connectivity changes (before P value correction) was much higher in the stimulation group (29.71%) than in the control group (7.03%). The functional connectivity of the bilateral prefrontal lobe and between cerebral hemispheres in the stimulation group was decreased after the experiment compared with before the experiment (P’＜0.05 after Bonferroni correction), but there was no significant change in the control group.Conclusion Repeated tDCS can improve the connectivity efficiency of prefrontal cortex by reducing the strength of functional connectivity.