Abstract: Objective　To study the relationship between serum pepsinogen (PG) Ⅰ/PGⅡ ratio with various gastric diseases, and provide the reference for screening in the early diagnosis of gastric cancer.   Methods　Chemiluminesent microparticle immunoassay was used to determine the levels of PGⅠ and PGⅡ and the ratio of PGⅠ/PGⅡ in 145 patients with various gastric diseases. The results were analyzed statistically.  Results　Compared with patients with chronic nonatrophic gastritis,the serum PGⅠ/PGⅡ ratios in patients with gastric ulcer and atrophic gastritis were lower (P<0.05), and that in patients with gastric cancer was significantly lower (P<0.001). There was no statistical significance of PGⅠ/PGⅡ ratio among atrophic gastritis, gastric cancer and gastric ulcer (P> 0.05).  Conclusions　The changes of serum PGⅠ/PGⅡ ratio are related with gastric pathological changes, and the PGⅠ/PGⅡ ratio has a clinical significance for the early screening of gastric cancer and gastric precancerosis.