The present disclosure provides a modular sectional sofa, including a bottom frame, a backrest frame and a cushion, wherein the inner side surface of the backrest frame is provided with a hook body, the hook body comprises a connection element, the lower surface of the connection element is provided with an inserting part, the upper surface of the bottom frame is provided with a hole or slot, when the inserting part is connected to the hole or slot, the backrest frame is connected with the bottom frame into a whole. A modular sectional sofa is further provided, including a bottom frame and a U-shaped connection element, wherein the U-shaped connection element connects two bottom frames through a left position limiting post and a right position limiting post. A modular sectional sofa is further provided, the side edge on the upper surface of the bottom frame is provided with four holes or slots, and the hook body on the inner side surface of the backrest frame are connected in any two holes or slots, and the backrest frame is connected with any side of the bottom frame. This reduces the size and the weight of sofa to improve the convenience of sofa handling. There are a variety of combinations. The present disclosure is strongly stable after assemble and convenient for people to use.