The invention relates to an oil drain valve anti-theft cover of a box-type substation to solve the problem that in the prior art, transformer oil of the box-type substation is stolen from an oil drain valve. The anti-theft cover comprises a shell and clamping claws on the shell. The clamping claws are provided with clamping parts which are used for being hooked onto the inner side face of an external end flange of an oil drain valve. The clamping claws include movable clamping claws which are movably arranged on the shell, and the movable clamping claws are provided with locking stations which are hooked to the inner side face of the external end flange and unlocking stations which are separated from the external end flange. When the movable clamping claws are located on the locking stations, the anti-theft cover is locked to the external end flange of the oil drain valve. The shell is internally provided with a rack and pinion mechanism, a locking piece and a locking piece unlocking mechanism. The rack and pinion mechanism drives the movable clamping claws to move between the locking stations and the unlocking stations, the locking piece stops the rack and pinion mechanism from driving the movable clamping claws to move towards the unlocking stations, and the locking piece unlocking mechanism is in linkage with a key to unlock the locking for the movable clamping claws, and the anti-theft purpose is achieved.