The high-precision trajectory data of the rocket vertical take-off phase can be used to evaluate the technical performance and accuracy of the rocket, provide data reference for the improved design and finalization of the rocket, and also provide important trajectory reference data for the rocket take-off safety control system. The trajectory of the rocket in the vertical take-off phase changes greatly in the vertical rising direction, while the theoretical trajectory in both directions of the horizontal plane does not change. However, in the actual launch process, due to various interferences and certain delays and deviations in the real-time control of the rocket, the actual trajectory of the rocket in the horizontal plane will inevitably have a certain offset.The traditional trajectory measurement methods in the vertical take-off phase of rocket mainly include telemetry, optical and radio radar measurement. Due to the vibration caused by rocket launch, the trajectory measurement accuracy of telemetry system is not high, and it is difficult to obtain effective original analysis data after rocket failure. The optical measurement system uses images taken by multiple stations to obtain the rocket trajectory data after the rendezvous, but it is easily affected by the weather and has poor real-time performance. Due to the interference of ground clutter, it is difficult for radio radar to obtain effective trajectory data at this stage. It can be seen that there is no real-time trajectory measurement data in the vertical take-off phase of the rocket at present, and it is urgent to fill the data gap in this phase through new measurement methods.A single lidar can be used to measure the rocket trajectory in the take-off phase, but the trajectory data of the rocket in both directions of the horizontal plane in the vertical take-off phase changes very little, and only relying on a single lidar to measure the trajectory in the two directions will cause large errors. Compared with a single lidar measurement system, the field of view of the two multi-line lidars in the vertical direction can reach 25°, and a total of 128 laser scanning lines scan the rocket target area at the same time. In addition, the two lidars conduct fusion measurement at an intersection angle of 70°, which can cover the target area of the rocket with a larger angle range. Therefore, more target measurement points can be scanned, which can not only improve the fitting accuracy of the center of the ellipse, but also effectively ensure the reliability of the data measurement.In view of the difficult technical problem of obtaining real-time high-precision trajectory data in the rocket vertical take-off phase, a new rocket take-off phase trajectory fusion measurement system based on lidar is proposed in this paper, which has the advantages of convenient station layout, easy installation and low power consumption. At the same time, it is less affected by weather, ground clutter signals and rocket vibration, and can effectively obtain the rocket real-time trajectory data. Two lidars are installed on a two-dimensional precision turntable to form a fusion measurement system. Before the launch of the rocket, the two lidars jointly scan the middle and upper target areas of the rocket. Based on the proposed algorithm of laser point cloud data correction, the initial value solution of rocket target area trajectory and data fusion processing of the two trajectory data, the static and dynamic trajectory measurement accuracy of the lidar are calculated and analyzed to be 0.023 5 m and 0.036 6 m respectively. In the process of rocket vertical take-off, the two-dimensional precision turntable receives the trajectory data of the rocket target area in real time, guides the lidar to track and scan the whole process of the rocket vertical take-off phase with high precision according to the rocket position information, and completes the real-time and high-precision trajectory measurement of the rocket vertical take-off phase, which effectively fills the gap of the trajectory measurement data of the rocket at this stage and ensures the safety of rocket launch. Up to now, the rocket real-time trajectory measurement system based on lidar has successfully completed many test tasks in a satellite launch center. Under the conditions of vibration, tail flame and other environmental interference in the rocket take-off phase, the real-time dynamic trajectory measurement accuracy can be better than 0.05 m. It is verified that the measurement system and method proposed in this paper can effectively improve the measurement accuracy and reliability of rocket trajectory, which has important engineering application value.