For large-scale data center network, how to monitor the network effectively, discover the bottleneck of network performance and potential point of failure, provide support for optimization of network performance becomes the new research subject. However, there are many factors which affect the network performance, and there are differences in the influence of performance factors. How to give an accurate performance evaluation has been a difficult problem. To solve these problems, a network performance evaluation index system was proposed in this paper. On this basis, a method for evaluating the network performance of data centers based on objective weight (PE-OWD) was put forward. By using the method of objective weight determination, the dynamic calculation of the weights of the indexes was adopted. And using the data normalization method based on historical parameters, a perfect network performance evaluation model was established. For the Tianhe2 real network environment, the performance indexes of the network equipment were evaluated, and the validity of the method for evaluating the network performance was verified.