The invention relates to a novel wavelength division multiplexing demultiplexing optical assembly applied to high-speed parallel long-distance transmission. The output end of a laser group is sequentially provided with a lens group, an optical regulating plate group, a lower layer silicon lens array and a lower layer optical filter group, wherein the output end of the lower layer optical filter group is provided with a lower layer free space wavelength division multiplexing device, the output end of the lower layer free space wavelength division multiplexing device is provided with an optical isolator, the output end of the optical isolator is provided with a focusing lens, the output end of the focusing lens is connected with an input optical fiber, an output optical fiber is connected with a collimating lens, the output end of the collimating lens is connected with a prism, the output end of the prism is provided with an upper layer free space wavelength division multiplexing device, the output end of the upper layer free space wavelength division multiplexing device is provided with the upper layer optical filter group, the output end of the upper layer optical fiber group is provided with an upper layer silicon lens array, and the output end of the upper layer silicon lens array is provided with a detector group. The optical signal multiplexing and demultiplexing is realized by using the optical filter array structure.