In the process of RYGB surgery induced NASH improvement, the possible key genes are IGF1, JUN, FOS, LDLR, TYROBP, DUSP1, CXCR4, ATF3, CXCL2, EGR1, SAA1, CTSS, and PPARA, and the possible involved pathways are IL-17 signaling pathway, osteoclast differentiation pathway, chemokine signaling pathway, viral protein interaction with cytokine and cytokine receptor pathway, Toll-like receptor signaling pathway, TNF signaling pathway and mineral absorption pathway. The gene discussed is CTSS; the disease is metabolic dysfunction-associated steatohepatitis.