This paper briefly describes the working process of the computer-controlled ignition system of the engine: during the engine working, each sensor constantly detects the engine speed, supercharging, coolant temperature, intake temperature and other signals. These detection results will be input to the control unit after shaping, signal processing, analog-to-digital conversion and corresponding interface circuits. The control unit calculates according to the calculation method specified in the program, and converts the calculation result into a control signal when the primary circuit of the ignition coil is on or off. The control unit then outputs an instruction to turn off the primary circuit of the ignition coil and turn on the secondary circuit to generate high-voltage power. These high-voltage power will be transmitted to the spark plug through the distributor to ignite the combustible mixture. The control unit will continuously detect the signal input by the knock sensor and carry out closed-loop control to make the system work stably.