Coverage rate is not only an important criteria to assess wireless sensor network but also a key research subject. An optimized coverage algorithm driven by probability model is proposed in this paper. The solution of expectation value of sensor nodes coverage and tolerance as well as the verification process of expectation value of first coverage of concerned target nodes are obtained by calculation of probability coverage model. Regarding network energy, communication path is optimized by means of scheduling policy of node state. As for decrement in node energy, the significance of existence for fitting functional limit is proven. Thus, the energy of sensor nodes matches effectively and the consumption of node energy is restrained. The relationship among coverage functions of sensor nodes in the optimized monitoring area is proven. The simulation experiment shows the proposed algorithm can improve the quality of coverage and the service of network, restrain the consumption of network energy, and prolong the network lifetime.