Sensor deployment is one of the most fundamental and important issues in wireless sensor networks. Most of the current researches are concentrated on deploying static sensors or mobile sensors to improve coverage. This paper proposes on-demand centralized deployment algorithms in a hybrid sensor network which consists of both static and mobile sensors. The key feature is that on-demand deploying process is started by an event-driven request. A mobile sensor will be selected to heal coverage hole, on account of the priority of the Hole and the distance between the mobile sensor and the Hole. According to selection mobile sensors strategy is preemptive or not, the algorithms can present the different advantages of reducing the moving distance or reducing the response time, respectively, i.e., it has a characteristic with adaptability. Simulation result shows that the proposed approach differs from previous methods in which average moving distance and network lifetime are both improved for deploying sensors.