In the double-layered mobile Peer-to-Peer (P2P) systems, peers are classified into two types, super peers and sub-peers; a super peer manages its subpeers. The communications are done mostly among super peers to reduce the network traffic in searching files. In mobile networks, reliability that guarantees communications among peers is one of the crucial factors. However, most of the previous P2P systems are evaluated under the 'static' mobile P2P environment where the number of peers is fixed and there are no dynamic joins and leaves. In this environment, performances cannot be evaluated correctly. In this paper, we propose two schemes, the avoidance scheme and the role changing scheme, to improve the reliability of a system in the dynamic mobile P2P environment. The experimental results show that the proposed schemes improve the communication failure rates by 3% and 5% over the system without them, respectively.