A hydraulic oil cylinder has a buffer sleeve (4), a rodless cavity sealing end face (1-2) and at least one throttle oil channel (3-1). The buffer sleeve (4) is sleeved on an additional section (3a) of a piston rod in the rodless cavity (2-2) and axially slidable along the additional section (3a) of the piston rod. The rodless cavity sealing end face (1-2) is provided in an oil cylinder cavity between a rodless cavity oil passing hole (1-1) and the termination of the rodless cavity end face of the piston for the retraction process of the piston rod (3), and enables to block the buffer sleeve (4) and attach to the first end surface (4-1) of the buffer sleeve thereby forming a sealing surface.