The invention discloses a direct connection device for a three-phase enclosed GIS bus and a transformer. The direct connection device comprises a transformer bottom plate, oil-gas casings, a disk insulator for supporting the GIS bus, and a GIS shell arranged between the transformer bottom plate and the disk insulator, wherein the oil-gas casings and the transformer bottom plate are integrally molded; the oil-gas casings are provided with transfer conductors which are used for making the oil-gas casings correspond to the positions of corresponding bus conductors, so that the oil-gas casings and the corresponding bus conductors are directly connected through corresponding middle conductors; and a fracture for installing one middle conductor is formed between each casing conductor and the corresponding bus conductor. The middle conductors are detachable, so that the middle conductors are not installed in a test. The direct connection device has obvious fractures, so that mutual influence is avoided in the test; and after the test, conductive connection of the enclosed transformer and the enclosed GIS bus can be achieved through the transfer conductors.