The present invention provides a bidirectional linkage single damping mechanism suitable for a leg exerciser. The invention includes a circular drive element, which shifts circularly to define a first section and a second section in opposite motion directions. A brake swinging arm, provided with a coupling end and a swinging end. The coupling end is connected with a treading rotation axis; and the swinging end is connected with either section. The two sections drive separately two drive pulleys. A bidirectional drive pulley assembly has two rotary pulleys and two drive pulleys connected by a unidirectional bearing. The bidirectional drive pulley assembly then drives a damping wheel assembly. With this invention, it is possible to provide a damping mechanism that can be connected with the leg exercisers for an improved resistance.