The CO₂ injection enhanced oil recovery technology (CO₂ EOR/EGR) in oil and gas reservoirs is a major component of the CCUS industry, which can achieve a win-win situation between economic and environmental benefits. Shale gas reservoir has unique geological and ground engineering advantages, and is one of the most potential practical options for carrying out CCUS. In this paper, the shale of one shale gas field in Sichuan Basin is taken as the research object, and the competitive adsorption experiment of multi-component gas is carried out. The effects of gas injection volume, injection timing, shut-in time, and huff and puff cycles on gas recovery have been studied through physical simulation methods. The results indicate that the higher the CO₂ content in the gas injection medium, the more significant the adsorption capacity advantage of gas on the shale surface during the adsorption process. The conditions for good huff and puff effect: CO₂ content in the gas injection medium is 80%~100%, gas injection rate is 0.2~0.3PV, lock-in time exceeds 6h, and injection timing is relatively late. The first huff - huff of recovery increased by 24.2% to 47.8%, which can fully leverage the throughput effect and achieve high efficiency. Single well numerical simulation shows that compared to wells without CO2 injection, the recovery rate can increase by 19.8%. This study provides an important reference for enhanced recovery of Shale gas reservoir by CO₂ huff - puff.