The commercial unmanned aerial vehicles (UAVs) have characterization of light-weight and low operating time. They are mostly used for photography and filming, and their main power source is lithium battery. The purpose of this project cooperated with ITRI's Mechanical and Mechatronics Systems Research Laboratories was to develop an UAV for exploration and spraying pesticides, which requires long-duration flying ability. As a result, lithium battery and gasoline engine with integrated starter generator were used to build a hybrid power system. In order to achieve high-efficiency usage of two power sources, rule-base and fuzzy control strategies were developed in this project. Based on the real-time states of the UAV, the proposed control strategies are able to derive the power split ratio for the two power sources. The controller was implemented through digital signal processor. By the integration of the voltage and current sensing circuits, various sub-systems and main system, the developments of the hybrid power system and controller were complemented for the UAV in this project.