The present invention provides a wavelength control method, a system thereof and a shutoff depth control circuit. The method includes: enabling a current temperature of TEC (6) to be rapidly stabilized at a target temperature through a closed loop control of hardware PID (8); allowing the shut-off depth control circuit (11) to operate when a burst driver (5) that drives a light emitting assembly (3) is standby or operating, providing an input to the light emitting assembly (3) through the shut-off depth control circuit (11) so that the light-emitting assembly (3) can emit the light that does not affect the normal operations of other ONU, the light emitted allows the light emitting assembly (3) to be warmed up, which enables the light emitting assembly (3) to quickly stabilize the emitted light within the bandwidth required by each channel of the system during the time period from a non-light emitting state to a light emitting state.