In wireless networks, when an access point or base station is not available, ad-hoc network becomes a feasible choice. Routing is an important issue in wireless ad-hoc networks. The design of a routing protocol may significantly affect the performance of data transmission in wireless ad-hoc networks. In our work, we study the design and performance of on-demand routing protocols in sparse networks, which has not been studied before. We choose DSR as the routing protocol for studying and analyze the drawbacks of DSR in sparse networks. We point out two problems of DSR in sparse networks and propose relative solutions. The performance evaluation results show that our solutions reduce network latency and packet loss ratio in most cases.