To handle the problem of low link utilization resulting from mixing online and offline traffic in one data center transmission network and separating them with a fix way in the same link, we propose a solution of offline traffic scheduling based on online traffic prediction. It firstly predicts online traffic needed to be guaranteed preferentially in link using an algorithm calling Sliding-k that combines EWMA and Bayesian changepoint detection algorithm. This customized algorithm can make prediction sensitive to a sudden change of network environment and reduce unnecessary re-adjustments when network environment is steady at the same time. Therefore, it can exactly meet the prediction demand under different network environments. After computing the remaining space for offline traffic according to online traffic prediction result and implementing dynamic bandwidth allocation, it uses an algorithm called SEDF that can consider both traffic deadline and size to schedule offline traffic. Experimental results reflect that Sliding-k can meet the prediction needs both when network mutation occurs and when network has no change and can simultaneously improve the accuracy of traditional EWMA algorithm. The combination of Sliding-k and SEDF can improve the utilization of data center links, so as to make full use of link resources.