The invention discloses a control method for automatic start and stop of a permanent magnetic direct drive draught fan master control system unit. A state machine switching method is used for achieving control over the start and stop process of a draught fan, states of the unit in the starting running grid connection process are divided into an initialization mode, a standby mode, a start mode, apre-acceleration mode, an acceleration mode, a grid connection mode, a shutdown mode and a service mode, and in the start process, every time when the unit reaches one mode, the corresponding controltarget is achieved in the mode, and after the motor rotation speed, the blade pitch angle and the delay time reach the set value, the unit enters into the next state machine mode. By means of the control method, automatic draught fan start and stop can be achieved according to the outside environment and the unit situation under the situation that the unit is unattended; and in the start and stopprocess, the master control system, a current transformer and a variable pitch system achieve collaborative control, and safe and stable running of the unit is finally guaranteed.