This paper presents a method for measuring the optical assembly results based on multi-beam biaxial LiDAR. This method analyzes the optical assembly parameters of a LiDAR system affecting the LiDAR operation, and an experimental measurement system is built using a collimator to simulate the infinity imaging field. An InGaAs infrared camera is used to take pictures of the laser spot from the LiDAR transmitter and receiver, and then fit the laser spot images with Gaussian equations to calculate the biaxial LiDAR optical assembly results. Finally, the possible effecting factors of LiDAR alignment results are analyzed. This method is experimentally proven to achieve the measurement of the optical assembly results of a large scale multi-beam LiDAR. The possibility of further optimizing the measurement method by shaping the transmit laser is also reported.