The invention discloses a lock with an idle lock cylinder. According to the lock, the idle lock cylinder comprises an outer sleeve body, an inner sleeve body, a lock plate group and a lock plate clamping device; when a wrong key is inserted into the lock, the lock plate clamping device is not limited to the lock plate group and the wrong key can only drive lock plates to idle in the inner sleeve body; when a right key is inserted into the lock, the lock plate clamping device is limited to the lock plate group and the unlocking can be achieved by utilizing the right key; a first driven side surface and a first height limiting top surface are arranged on the side wall of a lock hole of at least one first lock plate; a second driven side surface and a second height limiting top surface are arranged on the side wall of a lock hole of at least one second lock plate; the first driven side surface and the second driven side surface are staggered in a front-and-rear manner along the rotating direction of the lock plates; the first height limiting top surface and the second height limiting top surface are mutually staggered in an up-and-down manner along the radial direction of the lock plates; and a plurality of toothed parts are arranged on the key in a front-and-rear manner along the inserting direction of the key. The lock has the advantages that by utilization of the matching between the mutually-staggered driven side surfaces and the mutually-staggered height limiting top surfaces, enumerations for the key can be achieved; the structure of the key can be simplified; the cost is low; and the number of the enumerations can be increased.