Recently multi-channel multimedia broadcast systems on P2P network have emerged in applications such as long-distance education and multimedia broadcast television. With the conflict between huge amounts of streaming data and limited available bandwidth over the Internet seemingly irreconcilable, we observe 1) some channels demand disseminating rapidly, having no requirement for high presentation quality at receivers and 2) some channels expect better quality of service metrics such as bit rate and delay than others while bandwidth contention of multiple channels makes it difficult to realize. Existing proposals have not done enough work based on the two observations. In this paper, we propose DiffStream, a multi-channel dissemination strategy. In DiffStream, each channel disseminates partial streaming data instead of all, using MDC technology. Meanwhile, service differentiation is also achieved by treating different channels with varying priorities and regulating allocation of network resource to different channels in application layer. Furthermore, an extensive mechanism of vacant bandwidth preemption for improving bandwidth utilization is also raised. Experiments are constructed on NS2 and the results have demonstrated DiffStream’s effectiveness in achieving our design objectives.