The invention provides a method for quickly locking wavelength in an optical network unit (ONU) burst optical mode and a debugging system thereof. The method comprises the following steps: enabling an MCU to control the heating or cooling of a TEC through a DAC, dynamically setting a target temperature value to carry out temperature compensation before the laser temperature is stable, and ensuring that the wavelength error is within +/-100pm after 30 minutes of light emission; and constantly adjusting and controlling the magnitude and speed of the heating or cooling of the TEC based on the own temperature difference and temperature change rate of the laser after start-up. The wavelength of the optical waves emitted by the laser can be rapidly closer to the target wavelength due to the compensation of the temperature, and the time required for the laser to enter the working state can be effectively shortened.