Disclosed is a method for monitoring the wavelength of a tunable laser device of user by local OLT. The method is applied to a wavelength division multiplexing passive optical network framework. The framework comprises an ONU, a first athermal array waveguide grating, a transmission optical fiber, a second athermal array waveguide grating and the OLT, which are sequentially connected. ONU comprises tunable wavelength optical transmitters. The method comprises: starting handshaking is carried out between the OLT and the ONU; and the OLT carries out wavelength drifting monitoring during operation of the ONU. Wavelength adjustment can be carried out on the multi-channel tunable laser device in an external auxiliary monitoring environment, thus channel wavelengths of the multi-channel tunable laser device can be accurately controlled, and the requirement for calibration accuracy of channels of the tunable laser device at the ONU is greatly reduced.