This paper presents preliminary design of quad-rotor based flying anchor node for localization of wireless sensor networks. The electromechanical design of the quad-rotor was detailed, and a complementary filter based sensor fusion scheme was adopted. The cascade fusion scheme first fuses gyros' output with accelerometers' gravity observation and magnetometers' magnetic observation to estimate attitude, then fuses GPS output with accelerometers output and attitude to obtain velocity and position estimations. The simplified models of attitude dynamic were derived from mechanism analysis and system identification. With these models the attitude control system was designed. The experimental results have shown that the proposed system can achieve satisfying attitude tracking performance in real flight, thus can fulfill the autonomous flight requirements of flying anchor node.