Abstract: Based on the k-ω SST model and γ-Re_θ transition model, a study was conducted on the flow characteristics around a square cylinder respectively at the Reynolds number of 1.4×10⁴ and 2.2×10⁴, so as to calculate the drag coefficient and Strouhal number of the square cylinder, analyze its average velocity profiles, and finally to find out the calculation cost and precision of different turbulent models. Results show that compared with k-ω SST model, the γ-Re_θ transition model is more superior in calculation precision and cost, which is more effective in predicting the position and magnitude of the recirculation region behind the square cylinder, and in analyzing the reattachment of separated flows on side walls near the rear corner, and therefore is a practical model for engineering applications at high Reynolds numbers.