〔Abstract〕 Objective To investigate the expression of Specific protein1(SP1) in esophageal squamous cell carcinoma(ESCC) and adjacent normal tissues and its effect on the proliferation and apoptosis of ESCC cells. Methods The expression of SP1 protein in 121 ESCC tissues and 74 adjacent normal tissues was detected by immunohistochemistry. Chi-square test and Cox regression analysis were used to analyze the relationship between SP1 and clinicopathological parameters and survival prognosis of ESCC patients. SP1 siRNA(small interfering RNA) was constructed and transfected into esophageal squamous cell carcinoma Eca109 and EC9706 cell lines. Western blot was used to detect the expression of SP1 after transfection. The effects of SP1 on the proliferation and apoptosis of esophageal squamous cell carcinoma cells were detected by cloning assay, CCK-8 cell proliferation assay and flow cytometry. Results SP1 protein was expressed in the nucleus of esophageal squamous cell carcinoma tissues, and the expression rate of SP1 protein in esophageal squamous cell carcinoma tissues was significantly higher than that in adjacent normal tissues(χ2=20.568,P<0.01).Comparison between groups showed that the high expression rate of SP1 was higher in female(P=0.041), moderately or poorly differentiated(P=0.038) and T3-T4 invasion depth(P=0.041) ESCC(esophageal squamous cell carcinoma) patients. Log-rank test showed that the survival time of patients with high expression of SP1 was shorter than that of patients with low expression of SP1(P=0.048). Multivariate Cox regression analysis showed that TNM(tumor node metastasis classification) stage(Ⅲ+Ⅳ) was a potential risk factor for shorter survival time in patients with esophageal squamous cell carcinoma(P<0.001). Cell biological experiments showed that compared with the control group, the proliferation ability of esophageal squamous cell carcinoma cell lines decreased(P<0.05) and the apoptosis index increased(P<0.05) after silencing SP1. Conclusion SP1 protein is highly expressed in human esophageal squamous cell carcinoma tissues and is associated with poor prognosis in patients. Silencing SP1 can inhibit the proliferation of esophageal squamous cell carcinoma cells and promote their apoptosis.