Adequate coverage is one of the main problems for distributed wireless sensor networks and The effectiveness of that highly depends on the sensor deployment scheme. Given a finite number of sensors, optimizing the sensor deployment will provide sufficient sensor coverage and save power of sensors for movement to target location to adequate coverage. In this paper, we apply fuzzy logic system to optimize the sensor placement after an initial random deployment. Based on Voronoi diagrams and Fuzzy logic, we design two distributed algorithms for controlling the movement of sensors. Simulation results show that our approaches maximiz the sensor coverage.