A shadow fading caused by obstructions in the surroundings of transmitting has an important effect on wireless sensor networks. It makes an object to be probabilistic sensed by more than one node. An optimal geographical density control algorithm in wireless sensor network based on probabilistic was proposed. By choosing the optimal nodes, this algorithm reduced overlapping area that satisfies covered quality as much as possible to minimize working number. The simulation results show that this algorithm can minimize the total number of nodes.