Objective To study the effect of Xiaotan Jieyu (XTJY) Decoction on PI3K/Akt signal pathway of MCF-10AT cells of breast precancerous lesion and the ralated mechanism. Methods The MCF-10AT cells were randomly divided into following groups: XTJY group, PI3K/Akt inhibitor LY294002 (LY) group, XTJY+LY group and control (CON) group. After corresponding drug intervention, CCK-8 method was used to observe the MCF-10AT cell proliferation and growth inhibition at 24 h and 48 h, flow cytometry was used to detect the changes of cell cycle at 48 h, and the expression changes of PTEN, PI3K and Akt protein were detected by Western blotting analysis at 48 h. Results The proliferation of MCF-10AT cells were significantly inhibited at 24 h and 48 h in XTJY, LY and XTJY+LY groups, and the inhibitory rate of MCF-10AT cells in XTJY+LY group was significantly higher than those in XTJY and LY groups (P<0.05). Compared with CON group, the percentages of G₀/G₁ phase cells in XTJY, LY and XTJY+LY groups were significantly increased at 48 h (P<0.05), while the percentages of S phase and G₂/M phase cells were significantly decreased (P<0.05); besides, there were significant differences between XTJY+LY group and the other two groups (P<0.05). Compared with CON group, the expressions of PI3K and p-AKT protein in XTJY, LY and XTJY+LY groups were significantly decreased at 48 h (P<0.05), and the expression of PTEN protein was significantly increased (P<0.05). Conclusion XTJY prescription may exert inhibitory and apoptotic effect on MCF-10AT cells through inhibiting the PI3K/Akt signal pathway.