Streaming applications in P2P (peer to peer) networks are getting more and more popular. However, high degree of churning in peer populations due to wireless or mobility is a common problem, and it would result in a low delivery ratio and instable quality of received multimedia. In this paper, we propose a P2P multi-streaming scheme, called ConStream, to resolve this problem. In our scheme, the whole content is composed of multi-stripes, and each of the multi-stripes will be distributed to multiple multicast trees and be forwarded concurrently. In addition, we insert parity packets into streams so that clients can recover lost data. One merit of the proposed approach is that the transmission rate of each stream in our ConStream is only half of that in the traditional single streaming. Simulation results show that the proposed ConStream has a higher delivery ratio than Scribe-PRM and SplitStream under various MTTFs (mean time to failures).