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.