A cash box (1) used for storing cashes and provided with a self-locking mechanism comprises a box body (11), a box door (12) and a box door self-locking mechanism. The cashbox (1) is arranged on a cashbox bracket (3). The box door self-locking mechanism comprises a lock (21) for locking the box door (12) and a door switch structure (22) which is fixed on the cashbox bracket (3) and used for opening or closing the box door (12). The lock (21) comprises a movable lock tongue (211) connected with the box door (12) and a lock cylinder (212) which is fixed on one wall of the box body (11) and movably buckled with the movable lock tongue (211). A triggering element which acts on the door switch structure is arranged on the box door (12) which is opened by the door switch structure when the box body (11) is pushed into the cashbox bracket (3) and which is locked by the door switch structure when the box body (11) is drawn out of the cashbox bracket (3). The cashbox has self-locking function while being forcedly dismantled and ensures the safety of articles inside the box while being displaced and transported.