Based on probabilistic sensing model, this paper investigates the issue of barrier coverage in order to solve the problem of barrier coverage in wireless sensor network. By analyzing the cost and the power consumption of sensor nodes and adopting the data fusion technique within adjacent nodes, the paper brings forth an optimized deployment strategy for barrier coverage when the speed of mobile target is lower than the critical speed. It also presents the critical condition for the strategy to apply. The analysis and simulation results show that the proposed strategy can effectively improve the lifetime of the network.