In order to study the interaction law of Ji dense conglomerate with CO2 and water, based on the reservoir conditions of Mahu dense conglomerate reservoir in Junggar Basin, we carried out experiments on the interaction of dense conglomerate with CO2 and water. The results show that CO2 dissolved in water generates carbonic acid, which mainly interacts chemically with feldspar and calcite in the intergranular cement of dense conglomerate to form a strong erosion phenomenon around the gravel, which is dominated by erosion and supplemented by sedimentation, and ultimately increases the rock porosity and permeability, and strengthens the seepage capacity of reservoir fluids, with the maximum increment of porosity and permeability being 3.65% and 87.36%, respectively. At the same time, the roughness of the rock surface increased after the action, the hydrophilic mineral quartz was exposed on the surface, and the hydrophilicity of the rock was enhanced by decreasing the wetting contact angle of the water phase by 7.4°. It has a positive effect on CO2 throughput to improve crude oil recovery, and the main oil increase mechanism includes the following two points: one is to increase the pore space to improve the fluid seepage capacity; and the other is to improve the rock water-phase wettability to improve the reservoir water-phase seepage and absorption capacity and crude oil flow capacity, so as to improve the crude oil recovery.