The pSilencer4.1-B7-H4-shRNA and pSilencer4.1-scrambled shRNA vectors were converted into the HT-29 cells by liposome method as B7-H4 shRNA group and scrambled shRNA group. The expression levels of B7-H4 mRNA in the HT-29 cells in two groups was detected by RT-qPCR method； the expression levels of B7-H4 protein in the HT-29 cells in two groups were detected by Western blotting method； CCK-8 method was performed to detect the proliferation activities of the HT-29 cells in two groups；flow cytometry was used to detect the percentages of HT-29 cells at different cell cycles and the apoptotic rates of the HT-29 cells in two groups； Transwell chamber assay was used to measure the number of migration cells of the HT-29 cells in two groups； the levels of matrix metalloproteinases 2（MMP-2）and matrix metalloproteinases 9（MMP-9）in liquid supernatant of the HT-29 cells in two groups were detected by ELISA assay；the expression amounts of Bcl-2 and Caspase-3 in the HT-29 cells in two groups were detected by Western blotting method；the expression levels of B7-H4 mRNA in HT-29 cells before and after inhibiting the PI3K/Akt/mTOR signal pathway were analyzed by RT-qPCR method；Western blotting method was used to detect the expression levels of B7-H4 protein in the HT-29 cells before and after inhibiting the PI3K/Akt/mTOR signal pathway.

The expression levels of B7-H4 mRNA and protein in the HT-29 cells in B7-H4 shRNA group were significantly lower than those in scrambled shRNA group （P<0.01）. Compared with scrambled shRNA group， the proliferation ability of the HT-29 cells in B7-H4 shRNA group was decreased （P<0.05）， and the percentages of cells in G₀/G₁ phase and S phase had were no statistically significant differences（P>0.05）， the apoptotic rate and the expression level of Caspase-3 protein in the HT-29 cells were significantly increased （P<0.05）， the expression level of Bcl-2 protein was significantly decreased （P<0.05），the number of migrating cells was decreased （P<0.01）， and the levels of MMP-2 and MMP-9 were also significantly decreased （P<0.05）.Compared with control group， the expression levels of B7-H4 mRNA and protein in the HT-29 cells in LY294002 group and rapamycin group were significantly decreased（P<0.05）.

Silencing of B7-H4 expression can significantly inhibit the proliferation， apoptosis and migration of the HT-29 cells， and its mechanism may be related to the activity of PI3K/Akt/ mTOR signaling pathway.