In this research, a sway suppression algorithm was developed for a crane operator support system. To evaluate the effect of sway suppression, a crane experiment testbed was manufactured. The crane testbed is designed by the crane dynamic model, and the swing motion, boom motion and load hoisting are driven by the electric motors. The validity of the dynamic model for a crane was verified by the testbed experiment. The algorithm for sway suppression is consisted of the open loop control based on the phase plane theory, and was implemented in the testbed. The effect of sway suppression was verified by the testbed, and the effectiveness of algorithm was confirmed.