The invention relates to a method and a system for self-locking and fixedly connecting a thin plate. The connecting system is provided with a self-locking rivet with a cylinder rod part with a pointed circular ring at the lower end of the cylinder rod part, a blank holder outside the rivet, the thin plate to be connected, and a female die with an annular groove in the lower part of the female die; the thin plate to be connected has two to three layers, and the elongation rate of the lowest layer is more than or equal to 12 percent; the thickness and the strength from the lowest layer to the top layer are gradually reduced; and the thickness of the lowest layer is more than 1 / 3 of the tot l thickness. When a self-locking riveting tool is used, a drive punch hammer and the blank holder pre-press the thin plate, and the self-locking rivet stabs the thin plate after pressurization, so that the lower part of the thin plate is subject to plastic deformation towards the inner part of the annular groove; and a mechanical self-locking structure is formed after expansion. According to the method and the system for self-locking and fixedly connecting the thin plate, a problem that the thin plate cannot be subject to spot welding can be solved; punching and riveting can be achieved at one time, the efficiency is high, and a time cycle for connecting one rivet is three seconds; products can be manufactured without smoke, gas, spark, dust, scraps and noise, and requirements on connection, automatic mass production and environmental protection of automobile light materials; and the connecting method and the system can be used for the fixed connection of thin aluminum plates, metal and non-metal, painted or cladded ferrous metal and the like.