The invention discloses a UDWDM-PON transmitter based on the wavelength automatic locking and tracking technology. The UDWDM-PON transmitter includes a laser, an attenuator and a first 1x8 coupler which are connected in sequence to a microwave source; 8 channels are formed after the first 1x8 coupler. All the channels are concentrated on an optical fiber through a second 8x1 coupler; the laser isa mode-locked laser; the first, third, fifth, and seventh channels are odd-numbered channels, and the second, fourth, sixth, and eighth channels are even-numbered channels. The odd-numbered channels are used as the downlink optical carrier to carry the downlink data, and the even-numbered channels are used as the uplink optical carrier to complete the transmission of the user information. An optical frequency comb generated by the mode-locked laser is used as a wavelength reference, and the injection locking is performed on the plurality of DFB lasers to complete the separation of the wavelength reference, so that the problem of wavelength synchronization in the access network is solved; and selective modulation is performed on the separated multiple channels to track the wavelength reference of the mode-locked laser, and the stability of the small channel spacing in the access network can be ensured.