Abstract: For landing on Mars for inspection detection，a tri-folded and deployed ramp is proposed to transfer the Mars rover from the landing platform to the Mars surface safely. The uncertainty of the transfer attitude is the difficulty of tri-folded and deployed ramp. The minimum length of ramp is analyzed according to Martian topography to ensure the transfer safety of Mars Rover. The length of tri-folded and deployed ramp is optimized to meet the requirements of the minimum length of ramp. The results can provide reference for the mars rover transferring project of China.