The utility model discloses a safe and reliable error power transmission prevention device for a house-free main switch. The switch mainly comprises a main switch and baffles located on two sides of the main switch. The main switch is provided with an operating handle used for switching on and switching off. A pair of limiting holes corresponding in position are formed in the positions, located inthe middle of the operation handle, of the baffles on the two sides, the outer side wall of the baffle on one side is connected with a limiting piece through a chain, the limiting piece can be inserted into the limiting holes, the end, connected with the chain, of the limiting piece is provided with a protruding part which cannot penetrate through the limiting holes, and the end, away from the chain, of the limiting piece. The locking device is simple in structure, convenient to use, safe and reliable, when elevator maintenance personnel need to lock the off state of the main switch, only thelimiting piece needs to be inserted into the limiting hole, then the padlock is used for locking the lock hole, and the use safety of the elevator maintenance personnel is guaranteed.