〔Abstract〕 Objective To explore differential expression of insulin like growth factor 1(IGF1) in oral squamous cell carcinoma(OSCC) tissues and cells, and to analyze its clinical significance of IGF1. Methods The protein expression of IGF1 was detected in 115 OSCC tissues(OSCC group) and 74 normal tissues(normal group) using immunohistochemical technique, and the relationship with the clinicopathological factors and prognosis of OSCC was analyzed. The IGF1 protein and mRNA levels in HOK and OSCC cell lines(CAL-27, TCA-8113, SCC-15 and SCC-25) were detected by Western blot and qRT-PCR.Results The high expression rate of IGF1 in OSCC group was 72.17%, which was significantly higher than that in normal group(2.70%)(P<0.001). The proportion under ROC curve(AUC) of OSCC diagnosed by IGF1 was 0.81, the sensitivity was 0.73, and the specificity was 0.82. The expression of IGF1 was related to the degree of differentiation, T stage and depth of invasion(P=0.03,P=0.02,P=0.02), but not to gender, age, N stage, TNM stage, smoking, alcohol consumption, or HPV infection(P>0.05). Kaplan-Meier and COX regression analysis showed that the high expression of IGF1, the degree of differentiation, the T stage and the depth of infiltration were the related factors affecting the prognosis of patients(P<0.01,P=0.04,P=0.03,P=0.04). COX multivariate indicated that high expression of IGF1 was an independent factor affecting the prognosis of patients(P=0.01). Western blot and qRT-PCR results indicated that the expression of IGF1 in OSCC cell lines was higher than that in HOK(P<0.05).Conclusion IGF1 can be a potential diagnostic and poor prognostic marker in oral squamous cell carcinoma.