A stepping down trajectory planning method as well as a robot using the same and a computer readable storage medium are provided. The method includes: dividing a stepping down process of the robot into a plurality of planned stages; adjusting a start position of a swing leg of the robot according to an ankle-to-heel distance, where the ankle-to-heel distance is a horizontal distance between an ankle joint of the swing leg of the robot and a heel of the swing leg of the robot; determining an initial state and an end state of the swing leg in each of the planned stages according to the start position; and obtaining a planned trajectory of the swing leg by performing a curve fitting on the swing leg in each of the planned stages the initial state and the end state.