For CO2 hydrogenation over the graphene oxide (GO) modified In2O3 catalysts, GO promoted the transformation from cubic In2O3 (c-In2O3) to hexagonal In2O3 (h-In2O3). The c-In2O3(440)/h-In2O3(110) homojunction was formed between h-In2O3(110) and c-In2O3(440). The homojunction strengthened the interaction between the two phases, motivated the reduction of surface In2O3 and facilitated the generation of oxygen vacancies, which was greatly beneficial to the formation of methanol. Display omitted •GO promoted the transform of c-In2O3 to h-In2O3 and inhibited the deep reduction of h-In2O3 to In.•The formation energy of oxygen vacancies on homojunction was lower than that of h-In2O3 or c-In2O3.•The highest STY of methanol could reach 0.93 gMeOHh−1gcat−1 on In2O3-8 wt% GO under 3 MPa and 350 °C.•The homojunction formed by c-In2O3(440) and h-In2O3(110) was conducive to the methanol formation. The graphene oxide (GO) modified In2O3 composite catalyst was applied for CO2 hydrogenation to methanol. The GO significantly promoted the formation of hexagonal In2O3 (h-In2O3) and inhibited the deep reduction of h-In2O3 to element In. The homojunction formed by h-In2O3(110) and c-In2O3(440) strengthened the interaction between the two phases, motivated the reduction of surface In2O3 and facilitated the generation of oxygen vacancies, which was greatly beneficial to the formation of methanol. DFT manifested that the formation energy of oxygen vacancies on c-In2O3(440)/h-In2O3(110) homojunction was lower than that of single h-In2O3 or c-In2O3, indicating that more oxygen vacancies were easier to be generated at the two phases interface. For rod In2O3 catalysts modified by different GO content, when the GO content reached 8%, the space–time yield (STY) of methanol could be as high as 0.93 gMeOHh−1gcat−1, and the methanol selectivity could still reach more than 76% with CO2 conversion of 10.4%.