The invention discloses an induced draught fan and boost fan combined control method for a large thermal generator set. The thermal generator set comprises at least two induced draught fans and at least two boost fans. The control method includes the following portions, namely, stripping protection logic optimization of the induced draught fans and the boost fans, sequential control start step sequence optimization of the induced draught fans and the boost fans, the steps of the induced draught fan and boost fan combined control method in the normal running process, and the steps of the induced draught fan and boost fan combined control method under the abnormal working condition. By means of the method, the influences on pressure at the inlet of the FGD can be reduced when the boost fans are started; working condition changes can be responded to in time in the running process of the set; running of the set can be ensured by conducting adjustment in time through the RB method and other methods under the accident working condition; when device safety is influenced, interlocked stripping of the induced draught fans and the boost fans can be achieved, and the method has great significance in safe, stable and optimized running of the set.