In this paper, we propose an approach to autonomously control a quadrotor micro aerial vehicle (MAV). With take-off weight of 50 g and 8-min flight endurance, the MAV platform codenamed ‘KayLion’ developed by the National University of Singapore (NUS) is able to perform autonomous flight with pre-planned path tracking. The vision-based autonomous control is realized with a light weight camera system and an ultrasonic range finder integrated to the MAV. An optical flow algorithm is adopted and processed on ground control station to provide position and velocity estimation of the MAV. A model-based position controller is implemented to realize autonomous flight.