Abstract: Some types of arthropods can go through rugged terrains high-efficiently and stably, which gives us innovative ideas and adequate theories for designing bionic legged-robots or mobile platforms. Therefore, the biomechanics analysis of legged-animals during their locomotion on a terrain is highly significant in many biological or biorobotics disciplines. The locomotion mechanism of the Chinese mitten crab, which originated from the Far East and predominantly lived along rocky shores or in freshwater, as a typical arthropod, was studied using the experimental methods of biomechanics. In the present study, 30 tested Chinese mitten crabs (Eriocheir sinensis Milne-Edwards) were collected from Yangcheng Lake in China. The body mass of the crabs was measured with an electronic balance (accuracy=0.001 g) and the location of the center of mass on the dorsal carapace for each crab was determined with a suspended test. In order to capture the video images of the movements of Chinese mitten crabs' locomotion on a smooth terrain, we designed a high speed 3-D (three-dimension) including four high-speed cameras with recording speed of 120 frames/s and a resolution of 640 pixel×480 pixel, four LED video lights with a color temperature of (5500±200) K, a flash light to produce a flash signal which was captured simultaneously by four high-speed cameras as the starting point to analyze the video images in the motion analysis system, and a 0.6 m×0.4 m×0.2 m calibration frame with 16 non-linear points that approximately filled the overlapping region of the four cameras before the experiments. Frame-by-frame analysis of the motion video images was performed using a SIMI-motion analysis system and all kinematic parameters of the center of mass could be obtained from the analysis system directly. The typical variables, such as mechanical energy, the shift phase between the undulations in kinetic energy and gravitational potential energy, percentage recovery, and mass-specific rate of the mechanical power of the center of mass were calculated from kinematic parameters. The statistical results of the phase shift between the undulations in kinetic energy and gravitational potential energy show that the Chinese mitten crab used a bouncing gait as the main energy-conserving and -releasing pattern of mechanical energy when moving on a smooth terrain. The undulations of kinetic energy, gravitational potential energy, and total mechanical energy of the center of mass of the Chinese mitten crab performed sinusoidal curves. The percentage recovery of Chinese mitten crabs with an approximate mean value of (31.73%±17.29%), which was lower than that of ghost crab (Ocypode quadrata, 55%-70%) and different from death-head cockroach (Blaberus discoidalis, the mean value is 15.7%), did not vary as a function of average speed. Therefore, the relation between percentage recovery and average speed and the low percentage recovery also indicate that the bouncing gait was used by Chinese mitten crab for its main energy conservation pattern. The mass-specific rate of mechanical power increased with average speed linearly. The mass-specific rate of horizontal kinetic power was the main component of the mass-specific rate of kinetic power required to accelerate the center of mass of the Chinese mitten crab; the mass-specific of gravitational potential power was the main component of the mass-specific rate of total mechanical power required to lift the center of mass of the Chinese mitten crab.