The invention provides a combined lattice beam for an integrated framework of a 500kV transformer substation. The combined lattice beam comprises a first main beam, a second main beam, a third main beam, a first connecting plate and a third supporting part, the first connecting plate is respectively and fixedly connected on the first main beam, the second main beam and the third main beam, the first connecting plate is fixedly connected between the first main beam and the second main beam, between the second main beam and the third main beam and between the first main beam and the third main beam respectively through a third supporting part, and the first main beam, the second main beam and the third main beam collectively form a triangular structure. The combined lattice beam has high stability, high resistant-lateral rigidity, wind load resistance and anti-shake performance, the resistant-lateral rigidity, the wind load resistance and the anti-shake performance of the integrated framework can be greatly improved when the combined lattice beam is applied to the 500kV transformer substation, and safe and reliable running of the 500kV transformer substation is ensured.