As the most commonly and widely used dock leveler, the retractable dock leveler is easy to operate and has stable performance and low repair rate, which is particularly suitable for loading and unloading of double containers. The complete retractable dock leveler includes integrated hydraulic system, overall surgace structure, retractable tongue plate structure, open base, security feet guard plate and two pieces of standard anti-collision rubber, all of which are produced according to the EN1398 standards. The large platform is lifted by the master cylinder. Then the auxiliary cylinder pushes out the lip plate which will descend to the tail of the compartment.