The invention discloses an integrated vehicle body rear floor and a manufacturing method thereof. The integrated vehicle body rear floor comprises a floor body which is formed by compression molding,wherein a concave spare tire pool is formed by adopting a long fiber reinforced thermoplastic composite material in the middle of the floor body, a spare tire mounting point is arranged in the middleof the spare tire pool, buffer steps consisting of a continuous fiber reinforced thermoplastic composite material and a long fiber reinforced thermoplastic composite material is formed around the front side and the left side and right side of the spare tire pool, a front reinforcing beam, right longitudinal beam, rear reinforcing beam and left longitudinal beam consisting of the continuous fiber reinforced thermoplastic composite material are arranged around the top surface of the buffer steps. According to the invention, the combination of the long fiber composite material and the continuousfiber composite material is utilized, the advantages of good fluidity of the long fiber composite material and high strength and high modulus of the continuous fiber composite material are organicallycombined, the requirements of complex structure and high strength are considered, the front reinforcing beam, the buffer step, the spare tire pool, the right longitudinal beam, the rear reinforcing beam, the spare tire mounting points and the left longitudinal beam are integrally manufactured, so that the working procedures are reduced, the number of molds is reduced, and the cost is reduced.