Objective] To observe the diagnosis value of noninvasive diagnosis model S index used to evaluate the fibrosis degree of slight chronic hepatitis B(CHB). [Method] Trace back and investigate the routine serological indicators GGT, PLT, ALB and liver aspiration biopsy results of 63 cases of CHB;use noninvasive diagnosis formula to calculate:S index=1000×GGT/(PLT×ALB2),use ROC curve to analyze and evaluate the clinical diagnosis value of S index. [Result] S index is in positive relation with liver fibrosis degree. S index can forecast the fibrosis having or not with best truncation point 0.04h, the sensitivity 87.0%, specificity 47.5%and area under the curve(AUC) 0.690,close to 0. 7; in forecasting obvious fibrosis, with best truncation point 0.04h, sensitivity 100%,specificity 36.8%,AUC 0.664. [Conclusion] S index used for forecasting slight CHB having or not fibrosis has high value of diagnosis, but it has low correctness for diagnosing having or not obvious liver fibrosis.