In order to control the 5R manipulator to track arc trace or to avoid obstacles effectively, and avoid the discontinuity of joint angle in space, firstly, position interpolation of the arc motion trajectory of the Cartesian space is made. The inverse solution of position value was gotten in Cartesian space to joint space based on two kinds of artificial constraint mode. Then the least square solution of joint angle deviation was obtained by least square method (LSM). Finally, the trajectory of the end and the joints were simulated. The results show that the circular arc trajectory of the end of robot manipulator is smooth, and the joint angles change continuously and the motion is stable.