Resource discovery and locating is an important research area in Mobile Peer-to-Peer (MP2P). Among all kinds of lookup methods, using indices to accelerate search is popular because of its simplicity and efficiency. In indices algorithms, nodes keep indices over the data of all nodes within R hops of themselves, where R is known as the radius of the index. Indices with appropriate radiuses can reduce the number of requests and accelerate lookup processes. However, current indices algorithms, such as central index and local indices, all fall into impropriety and inefficiency under MP2P, because their static index radiuses, which are system-wide invariable parameters, conflict with the mobility of MP2P environment. In this paper, we present the Dynamic Indices (DIs) algorithm to implement an efficient search in MP2P, in which the radius of each index varies according to the mobility of its context. When the network environment is mobile, which means resources are greatly volatile, DIs shorten their radiuses to guarantee the correctness of references. While the environment is static, DIs enlarge. Tests show that in MP2P environment DIs can improve the searching and locating performance significantly.