An online algorithm of realtime collision avoidance and trajectory tracking for the manipulator endeffector is proposed in the framework of geometric mechanics in this paper. First, the gyroscopic force is introduced in the motion of endeffector to generate its collisionfree smooth trajectory in work space. Next, the corresponding smooth trajectories in the joint space are obtained by solving the inverse kinematics problem with the damped least square method. Finally, through the comparison with the classical RRT algorithm, the effectiveness of the proposed algorithm is illustrated by numerical simulations of a 6 DOF manipulator.