In recent years, cooperative communications are widely studied. Cooperative communications can obtain the space diversity as Multiple-Input Multiple-Output (MIMO) systems. In cooperative communications, the relay method is important as Decode-and-Forward (DF) and Decode-Amplify-Forward (DAF). The multi-relay cooperative communications can improve the system performance. In the multi-relay cooperative communications, the optimum packet splitting method is effective. Moreover, the multi-relay cooperative communications can more improve the system performance by using the Power Allocation (PA). However, the PA method requires large Feedback Information (FBI). To solve this problem, in this paper, the authors propose the optimum packet splitting method based on the time domain Channel State Information (CSI) in the multi-relay cooperative communication with DF and DAF.