In data centers, a large number of IT sever racks with different heat dissipation rates are arranged in multiple rows, leading to much higher per-unit heat release and therefore more uneven temperature distribution than in general buildings. This paper chooses a small-scale data center located in China to analyze the thermal environment for the operation of these critical equipments. The wind speed and temperature in the data center were measured, and a corresponding computer room model was established via computational fluid dynamics (CFD) simulation software. Based on it, the characteristics of flow field and temperature field of the data center were analyzed. The optimization methods for problem of uneven temperature distribution and chaotic air supply in the data center were proposed and verified by evaluation index. Furthermore, the return temperature index(RHI) increased from 0.918 to 0.93, the return heat index(RTI) reduced from 0.222 to 0.342.