CO2 hydrogenation to methanol is an important way to achieve the goal of "double carbon". In this paper,CuZnAlY catalyst wasmodified by adding different contents of Mg,and its effect on the performance of CO2 hydrogenation to methanol was systematicallystudied. XRD,TPR,TPD and XPS were used to analyze the structure of the catalyst. The results showed that the addition of Mg built asuitable alkaline site,enhanced the CO2 adsorption capacity,improved the CO2 conversion and methanol selectivity. Among them,CZAYM2.5 composite catalyst has the highest space-time yield. Under the conditions of T=250 ℃,P=3.0 MPa,GHSV=4000 ml mlcat h,reaction gas H2:CO2=3:1 (molar ratio),the CO2 conversion,methanol selectivity and methanol space-time yield reached 18.95%,51.49% and 0.1549 g gcath,respectively. Meanwhile,stability tests were carried out for 720 h at improved pressure P=5.0 MPa. Theresults showed that:the CO2 conversion reached 22.00%,the selectivity of CH3OH was about 63.00%,and the methanol space-time yieldwas about 0.2100 g gcath. The catalyst showed good stability.