Simple multifunctional chair and application method

The invention relates to a simple multifunctional chair and its application method. The simple multifunctional chair specifically contains a seat body and a backrest. The backrest is slab-shaped. The seat body contains a seat and legs below the seat. the simple multifunctional chair is characterized in that the seat body is connected with the backrest through a connecting piece which is formed by hinge joint of two support bars; the connecting piece is hinged to the backrest; the two hinge joint parts are both provide with an angle rotary fixation device respectively; one support bar of the connecting piece is hinged to the backrest; the other support bar of the connecting piece is detachably connected with the seat body; the legs are all provided with extension legs; and a structure between each extension leg and the corresponding leg is adjustable. A rotary fixed part and a support part can be designed for strengthening or replacing the angle rotary fixation devices at two places. When the chair is in use, parts or all structures are combined for use through adjusting structures among the extension legs, the connecting piece, the angle rotary fixation devices, the backrest and the seat body. Thus, functions of a chair, integrated table and stool, a bed desk and the like are realized. The simple multifunctional chair has a wide application range.