Objective To investigate the effect of signal transducer and activator of transcription 1 (STAT1) on cell cycle of glioma U251 cells and related mechanism. Methods We transiently transfected glioma cell U251 cells with pcDNA3.1-STAT1 using LipofectamineTM2000 transfection reagent. The cells were divided into Mock group (no transfection), empty vector group (transfected with pcDNA3.1) and STAT1 group (transfected with pcDNA3.1-STAT1). The expression of STAT1 in glioma U251 cells was detected by Western blot. Cell proliferation was detected by MTT. Cell cycle was detected by flow cytometry. Wound healing assay was used to detect cell migration. The expression of P53, P21, bcl-2 and Caspase-8 in transfected cells was detected by Western blot. Results Compared with Mock group and empty vector group, the expression of STAT1 protein in STAT1 group was significantly increased (P < 0.05), cell proliferation decreased significantly (P < 0.05), the percentage of cells in phase G0/G1 increased significantly, and cell migration ability decreased significantly. The expression levels of P53, P21 and Caspase-8 increased significantly (P < 0.05) while bcl-2 decreased significantly (P < 0.05). Conclusion The high expression of STAT1 could inhibit the proliferation and promote the apoptosis of human glioma U251 cells, and STAT1 could regulate the expression of multiple signal transduction molecules. STAT1 plays a key role in the occurrence and development of glioma.