The invention discloses a vehicle-mounted loading and unloading method for a container. The method for installing four sets of vehicle-mounted loading and unloading tools at the four corners of the container respectively include the steps that firstly, a support and a supporting leg are integrally assembled before leaving a factory, under the use condition, an upper lock plate is installed in a peach-shaped hole of a corner piece of the top corner of the container, and whether installation is conducted in place or not is confirmed; secondly, a lower hook of a lower clamping plate is installed in a kidney-shaped hole in a corner piece of the bottom corner of the container, and whether installation is conducted in place or not is confirmed; thirdly, an upper transverse arm and the upper lock plate are connected through a first pin shaft; fourthly, the support and the lower hook of the lower clamping plate are connected through a second pin shaft; fifthly, a motor drive assembly is connected with a speed reducing device on the support through a connecting device; and sixthly, a ball head at the bottom of the supporting leg is connected with the base. According to the vehicle-mounted loading and unloading method for the container, the loading and unloading efficiency of the container is improved; and in the site environment where working of large lifting equipment is not facilitated, the vehicle-mounted loading and unloading method for the container can effectively solve the problem that the site is limited, and cost is low.