With the increasing difficulty of oil & gas exploration and development in Northwest China, the choke manifold of drilling well control device is facing an increasingly serious problem of high-speed particle erosion. In order to predict the erosion rate of choke manifold and put forward protective measures, it is necessary to clarify the erosion behavior of its material 30CrMo steel. On the basis of ASTM-G76 standard, the erosion experiment of 30CrMo steel is conducted by using the air jet erosion tester. The nozzle diameter of the tester is 1.5 mm, and the nozzle is 10 mm away from the sample surface. The erosive agent is angular alumina particles with median particle size of about 50 μm. The particle mass flow rate in all tests is equal to 1.55 g/min (measured value). The impact velocity of particles is measured by the double disk method. Then the weight loss analysis, three-dimensional profile analysis and microscopic morphology analysis of the experimental results are carried out in proper sequence by using three-dimensional microscope, scanning electron microscope (SEM) and other equipments. The results of weight loss analysis show that the erosion rate decreases with the increase of impact angle (15°-90°), and increases with the increase of impact velocity (107-149 m/s ). The erosion rate equation of 30CrMo steel is established by using these experimental data. The results of 3D profile analysis show that the erosion area decreases with the increase of impact angle, and remains unchanged with the increase of impact velocity. The particles ejected by the nozzle have a small radial diffusion phenomenon. The erosion depth first increases and then decreases with the increase of impact angle (maximum at 60° impact angle), and increases with the increase of impact velocity. The factors affecting the erosion area are the impact angle and nozzle cross-sectional area, and the factors affecting the erosion depth are the erosion rate (material erosion characteristics) and the abrasive mass distribution density. The mechanism analysis shows that the ploughing mechanism is dominant for 30CrMo steel at low impact angle (15°, 30°); The mixing mechanism of ploughing, compaction and cracking is dominant at medium impact angle (45°), and the compaction and cracking mechanism is dominant at high impact angle (60°, 90°). The erosion mechanism is obviously different under different impact angles, and the erosion mechanism presents a regular transition phenomenon with the increase of impact angle. In addition, the erosion mechanism is not affected by the impact velocity. To sum up, the material removal mechanism of 30CrMo steel impacted by high speed solid particles is typical plastic material erosion behavior. The impact angle affects the erosion rate through erosion mechanism, and the impact velocity affects the erosion rate through particle impact energy. The erosion rate equation of 30CrMo steel is established, which can be directly used for the lateral comparison of erosion resistance of materials or the establishment and simulation of erosion CFD model. The erosion depth can be reduced by improving the erosion resistance of materials or reducing the abrasive mass distribution density.