In order to smooth the trajectory of a robot and reduce dwell time， a transition curve is introduced between two adjacent curves in three-dimensional space． G2 continuity is guaranteed to transit smoothly． To minimize the amount of calculation， cubic and quartic Bezier curves are both analyzed． Furthermore， the contour curve is characterized by a transition parameter which defines the distance to the corner of the deviation． How to define the transition points for different curves is presented． A general move command interface is defined for receiving the curve limitations and transition parameters． Then， how to calculate the control points of the cubic and quartic Bezier curves is analyzed and given． Different situations are discussed separately， including transition between two lines， transition between a line and a circle， and transition between two circles． Finally， the experiments are carried out on a six degree of freedom ( DOF) industrial robot to validate the proposed method． Ｒesults of single transition and multiple transitions are presented． The trajectories in the joint space are also analyzed． The results indicate that the method achieves G2 continuity within the transition constraint and has good efficiency and adaptability．