Receiver optical assembly and assembly method thereof

A receiver optical assembly includes: an optical platform, a receiver optical port and a wavelength division multiplexer being arranged along an optical path on the optical platform; a circuit board, a photodetector array being disposed on the circuit board; a mounting block, a focusing lens and an optical path shifter being disposed on t the mounting block, the mounting block being fixed on the circuit board, and the optical path shifter being placed above the photodetector array. Incident light containing a multi-channel optical signal enters through the receiver optical port, and the wavelength division multiplexer divides the incident light into a plurality of single-channel optical signal beams. The single-channel optical signal beams are coupled to photodetectors on the photodetector array after passing through the focusing lens and the optical path shifter on the mounting block.