Deep foundation pit support construction method

The invention discloses a deep foundation pit support construction method. According to the deep foundation pit support construction method, a top beam and a horizontal support are lifted to the position above of a zero-layer plate, a supporting system is not changed, a certain distance is reserved above a cast-in-place pile steel bar, and the top beam, the horizontal support and a supporting column are cast in a cast-in-place mode; finally, the support is removed after the zero-layer plate of a building is constructed. The foundation pit support construction method has the advantages that the technology is easy, the construction risk is low, the safety coefficient is high, and the construction progress is accelerated effectively.