Abstract：Chronic atrophic gastritis (CAG) is one main risk factor for gastric cancer，and the degree of atrophy is positively correlated with age and cancerization risk. Based on the theory of chronic disease entering collaterals，Professor XU Su believes that the core pathogenesis of senile CAG is qi deficiency and collaterals stasis， and the treatment should mainly focus on fortifying the spleen and boosting qi， and invigorating blood and unblocking the collaterals， so as to delay and reverse the process of atrophy and intestinal metaplasia，and prevent and treat cancer. On this basis，he created Jianpi Yuwei Decoction.