Abstract: The parallelism of the optical axes between multi-beam laser transmitting and receiving system is a critical parameter for ensuring the performance of laser radar systems. To address the extremely high-precision registration challenge of achieving better than 10 μrad parallelism for a 48-beam laser transceiver system, a high-precision alignment and testing method for transmitting-receiver registration was proposed. A measurement system for laser transmitting-receiving parallelism was constructed using a long-focal-length collimator and a beam analyzer. By accurately measuring the parallelism errors of the 48 laser beams, the spacing of the 48 receiving fibers of the receiving system was arranged and manufactured according to the measurement results to achieve high-precision alignment of the parallelism. A 20 m focal length collimator was applied to measuring a laser system with a divergence angle of 15 μrad for the transmitter and a reception field of view of 80 μrad. The achieved precision for aligning and measuring the parallelism of the multi-beam laser transceivers was 3.56 μrad. After alignment, the maximum measured parallelism error for the 48 beams was 8.81 μrad, demonstrating strong feasibility for practical engineering applications.