In view of clamping angle can be different when the rotating screw pliers is clamping the different drill pipe, the relation between clamping angle and radius of drill pipe was analyzed. The force situation of rotating screw pliers was confirmed after calculating the clamping angle. Some significant result such like the clamping force,thrust of cylinder and other aspects were got by means of analyzing the force situation.Three kinds of drill pipes were picked to calculate by formular deduced in former jobs. ADAMS was used to make simulation with rotating screw pliers.The result of simulation verify the correctness of analysis again. 