The invention discloses a single-cylinder single-piston type free piston linear generator. The single-cylinder single-piston type free piston linear generator comprises a generator, a two-stroke engine and an auxiliary motor, the two-stroke engine comprises a piston cylinder, a crankcase sleeve part, a piston, a connecting rod and a cylinder cover, wherein the piston is matched with the piston cylinder, the crankcase sleeve part is connected with the piston cylinder, the piston is connected with the connecting rod, the auxiliary motor is arranged between the generator and the two-stroke engine, the auxiliary motor is connected with the generator and the two-stroke engine, a motor left end cover is connected with the auxiliary motor, and a motor right end cover is connected with a generatorshell; and the auxiliary motor, the generator, the connecting rod and the piston cylinder of the two-stroke engine are coaxially arranged, and a predetermined axial distance is correspondingly arranged between the generator stator and the two windings which are closest to the axial direction of the auxiliary motor stator. The single-cylinder single-piston type free piston linear generator solvesthe problem of long switching response time of the working mode of the motor, ensures that the piston successfully reaches the specified position, and enables the free piston linear generator to stably operate.