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 . <EOS>