The present invention provides a wavelength division multiplexing/demultiplexing optical transceiving assembly based on a diffraction grating, which is an uplink optical emitting unit and a downlink optical receiving unit that comprise a laser chip array, a light receiving detector array, a first fast axis collimating lens, a second fast axis collimating lens, a first slow axis collimating lens, a diffraction grating, a slow axis focusing lens, a second slow axis collimating lens, an optical isolator, a coupling output lens, a coupling input lens, a coupling outputting optical fiber and a coupling inputting optical fiber. The wavelength division multiplexing/demultiplexing optical transceiving assembly solves the technical problem of sharing a diffraction grating to realize a wavelength division multiplexing/demultiplexing function, achieves the beneficial effects of better diffraction grating filtering property, smaller light path coupling loss and insertion loss correlative with wavelength, larger independent optical element sizes, and simpler assembly process, and is more suitable for manufacturing a multi-channel wavelength division multiplexing/demultiplexing optical transceiving assembly.