The utility model discloses an electricity-larceny-preventing junction box for a transformer. The electricity-larceny-preventing junction box for the transformer comprises a base installed on the transformer, wherein a terminal hole corresponding to an output terminal of the transformer is formed in the base; a mutual inductor sleeved on an output circuit of the transformer is arranged in the base; an upper cover is hinged on the base; locking devices are arranged between the upper cover and the base; the locking devices are arranged on three separable sides corresponding to the upper cover and the base; the mutual inductor is sleeved on an output wire of the transformer, and a connecting terminal of the mutual inductor is arranged downwards; a limit groove matched with the connecting terminal of the mutual inductor in a clamping installation manner is formed in the base. The electricity-larceny-preventing junction box with the structure for the transformer is reasonable in structure, not easy to deform after being locked, and capable of avoiding electricity larceny.