In order to address the challenge of achieving precise motion control based on real-time feedback signals in soft robot,a motion detection method for soft robot based on the hue of photonic crystal structural color sensors is proposed. The working mechanism of this method lies in the fact that when the soft robot moves, the color of the photonic crystal structural color sensor integrated on it will change. By detecting these hue changes through image processing techniques and utilizing the mapping relationship between hue signals and motion states, the tracking and monitoring of the soft robot's motion state can be achieved. The results of hue detection stability test show that the average hue values under different brightness and saturation are 179.97° and 179.67°, and the standard deviations are 0.51 and 0.36, respectively.