The invention discloses a digital control method, device and system of an air generator. The digital control method of the air generator comprises steps: receiving an operation instruction sent by an airplane control panel, obtaining inertia characteristics shown by the air generator at different rotating speed stages, analyzing the inertia characteristics through adoption of a PID controller, performing a PID output, performing a corresponding restriction and a corresponding correction on a fuel amount according to the PID output and an obtained main control parameter, adjusting a control current of an electro-hydraulic servo device, and controlling the air generator according to a preset fuel supply amount rule. The problems of complex hardware structure and low control precision occurring in an analog type control device are solved. Safety and reliability of the air generator are improved, the overshoot amount is small, the response time is fast, and dynamic performance is excellent.