Abstract: 【Objective】The purpose of the study was to clarify the effect of overexpressed cytokine signal transducer suppressor 1(SOCS1) gene on the expression of key signaling pathway(JAK/STAT) related genes in mammary gland development, and to provide reference for revealing the mechanism of SOCS1 gene regulating proliferation and apoptosis of porcine mammary epithelial cells. 【Method】The overexpressed vector pcDNA3.1-SOCS1 and the negative control vector pcDNA3.1-NC were constructed and transfected into porcine mammary epithelial cells, respectively. Then, cell proliferation was detected by CCK-8, cell cycle and apoptosis were detected by flow cytometry, and the expression changes of JAK/STAT signaling pathway related genes after transfection were detected by real-time fluorescence quantitative PCR.【Result】Porcine mammary epithelial cells were transfected with overexpressed vector pcDNA3.1-SOCS1 and negative control vector pcDNA3.1-NC, respectively. The relative expression of SOCS1 gene in the overexpressed vector pcDNA3.1-SOCS1 transfection group was extremely significantly higher than that in the negative control vector pcDNA3.1-NC transfection group(P<0.01, the same below). After transfection for 48 and 72 h, the OD value of porcine mammary epithelial cells in the overexpressed vector pcDNA3.1-SOCS1 transfection group was extremely significantly lower than that in the negative control vector pcDNA3.1-NC transfection group, indicating that the overexpressed vector pcDNA3.1-SOCS1 could effectively inhibit the proliferation ability of porcine mammary epithelial cells. The apoptosis rate of cells in the overexpressed vector pcDNA3.1-SOCS1 transfection group (36.15±0.92)% was significantly higher than that of the negative control vector pcDNA3.1-NC transfection group (30.55±0.35)%(P<0.05, the same below), and the rate of G1 phase cells in the overexpressed vector pcDNA3.1-SOCS1 transfection group was extremely significantly decreased, while the rates of S and G2 phase cells were significantly increased. Compared with the negative control vector pcDNA3.1-NC transfection group, except for JAK2, STAT3 and TYK2 genes, the relative expressions of 9 JAK/STAT signaling pathway related genes, including SOCS2, SOCS3, JAK1, STAT2, STAT5A, IL-6, PRLR, MCL1 and PIAS3, in the overexpressed vector pcDNA3.1-SOCS1 transfection group were extremely significantly increased. 【Conclusion】Overexpression of SOCS1 gene can inhibit the proliferation of porcine mammary epithelial cells and promote the apoptosis of cells and affect the expression changes of JAK/STAT signaling pathway related genes, thus playing an important role in the regulation mechanism of mammary gland development in pigs.