A sofa assembly comprising at least one sofa backrest connection structure, a sofa seat frame and a sofa backrest, wherein: - said sofa backrest connection structure comprises a first member and a second member, wherein: - said first member comprises a first base plate, two guide rails symmetrically arranged on the first base plate, and a limiting part which is arranged on the first base plate and located on the two guide rails, and the limiting part is provided with a clamping protrusion; - said second member comprises a second base plate and a first horizontal plate connected to the second base plate, the second base plate comprises an insertion part, and the insertion part is provided with a clamping hole matched with the clamping protrusion; - after the insertion part is slidably inserted into and fitted with the two guide rails, the clamping protrusion is clamped in the clamping hole; - said second base plate and said first horizontal plate are integrally bent and formed; - said sofa seat frame comprises two symmetrically arranged cross beams and two longitudinal beams connected with two said cross beams; - said first horizontal plate is connected with an upper surface of the longitudinal beams, and said first base plate is connected with said sofa backrest. - said sofa backrest connection structure comprises a first member and a second member, wherein: - said first member comprises a first base plate, two guide rails symmetrically arranged on the first base plate, and a limiting part which is arranged on the first base plate and located on the two guide rails, and the limiting part is provided with a clamping protrusion; - said second member comprises a second base plate and a first horizontal plate connected to the second base plate, the second base plate comprises an insertion part, and the insertion part is provided with a clamping hole matched with the clamping protrusion; - after the insertion part is slidably inserted into and fitted with the two guide rails, the clamping protrusion is clamped in the clamping hole; - said second base plate and said first horizontal plate are integrally bent and formed; - said first member comprises a first base plate, two guide rails symmetrically arranged on the first base plate, and a limiting part which is arranged on the first base plate and located on the two guide rails, and the limiting part is provided with a clamping protrusion; - said second member comprises a second base plate and a first horizontal plate connected to the second base plate, the second base plate comprises an insertion part, and the insertion part is provided with a clamping hole matched with the clamping protrusion; - after the insertion part is slidably inserted into and fitted with the two guide rails, the clamping protrusion is clamped in the clamping hole; - said second base plate and said first horizontal plate are integrally bent and formed; - said sofa seat frame comprises two symmetrically arranged cross beams and two longitudinal beams connected with two said cross beams; - said first horizontal plate is connected with an upper surface of the longitudinal beams, and said first base plate is connected with said sofa backrest.