The invention discloses a high-precision ignition system for a small-size gasoline engine. The high-precision ignition system comprises a trigger signal filtering processing module. The trigger signalfiltering processing module comprises a trigger coil. The two ends of the trigger coil communicate with an MCU, and the trigger coil is used for sequentially transmitting first trigger signals A, second trigger signals B and third trigger signals C to the MCU. The waveform interval time of every two adjacent first trigger signals A is the time value T required when a flywheel rotates by 360 degrees. The waveform interval time of each second trigger signal B and the corresponding third trigger signal C is the time value t required when the flywheel rotates by N degrees. According to the high-precision ignition system, the instant rotating speed, formed when the ignition time approaches, of the flywheel is obtained through calculation of the t; the ignition delay time obtained through the tmore approaches the actually-required value, and thus high-precision design of the ignition angle is achieved; and the control precision of the actual ignition angle on the engine is +/-1 degree.