We propose the way to incorporate synchronization-based control to a robotic suit for Standing up motion assist. And we use non-exoskeleton robotic suit to confirm the effect of synchronization-based control for standing up motion without sense of resistance. It was found that the muscle activation of the gluteus maximus muscle and biceps femoris muscle decreased during standing up under certain condition and the robotic suit synchronized human standing up motion. We suggested that synchronization-based control was effective for standing up motion assistance with no sense of resistance.