The invention discloses a permanent magnet synchronous range extension system all-working-condition control method. Compared with starting conducted by a small start motor carried by an engine, starting conducted by a permanent magnet synchronous motor has the beneficial effects that the calibrated rotation speed of ignition oil injection of the engine is increased, and the situation that oil consumption emission is severe in the engine low-rotation-speed starting process is avoided. When a range extender enters in a first stage of the starting working condition, the actual torque of the permanent magnet synchronous motor responds to the target torque and is monotonically decreased to 0 Nm along with the increase of the rotation speed, the mode of the motor is switched into a power generation mode, and the actual torque of the motor is used for balancing the resistance torque of the engine in the process. Due to the fact that the target torque and the actual torque of the motor are reduced to 0 before the combustion torque of the engine is generated, and the control mode of the motor is switched to the power generation mode from an electric mode, so that after the engine starts generating power, the actual torque of the motor serves as the load of the engine to be gradually increased, the rotation speed is kept stable, and therefore, the smooth switchover of starting to an idlespeed working condition can be guaranteed when the output torque of the engine is suddenly increased.