Gastric cancer is one of the most serious cancers all over the world. Gastric tumor initiating cells (TIC) account for gastric tumorigenesis and metastasis. Here we identified circGTIC1 as a highly expressed circRNA in gastric cancer and gastric TICs. circGTIC1 knockout inhibited the self-renewal of gastric TICs and metastasis, and its overexpression activated gastric TICs. circGTIC1 drove the expression of Sox8 and exerted its role via Sox8-dependent manner. circGTIC1 associated with Ino80 chromatin remodeling complex, and recruited Ino80 complex to Sox8 promoter, finally initiated Sox8 expression. Our work revealed a novel circRNA to regulate gastric tumorigenesis and gastric TICs, adding a new layer for gastric TIC regulation and circRNA functions. CircGTIC1 plays a central role in gastric TIC self-renewal and metastasis. circGTIC1 drives the expression of Sox8 through recruiting Ino80 complex to Sox8 promoter. circGTIC1-Ino80-Sox8 axis can be used for gastric tumor and gastric TIC targeting. Our work revealed a novel circRNA to regulate gastric tumorigenesis and gastric TICs, adding a new layer for gastric TIC regulation and circRNA functions