To address the steep production drop and limited recovery efficiency following large-scale fracturing in tight oil reservoirs at M Lake, this study systematically examines how key factors—namely CO2 slug size, shut-in duration, and the number of cyclic huff-and-puff operations—influence the performance of CO2 stimulation. The experimental results show that CO2 can reach the miscible state and the minimum miscible pressure is 26.4 MPa by simulating the reservoir and fluid conditions of MX well area, carrying out slim tube experiment and CO2 huff and puff physical model experiment. At a temperature of 74.8 °C, a round of injection of 0.5 PV of CO2, soaking for 2h, can further increase the recovery rate by 18.1 percentage points. The CO2 huff and puff test of horizontal well was carried out in #25 well in MX well area. The cumulative oil increase was 7517.1 tons, the oil change rate was up to 1:1.9, and the investment recovery period was 1.5 years. It provides a technical reference for further improving recovery of horizontal wells in tight reservoirs.