Abstract: The experimental research on the impact of 93 tungsten cylindrical projectile on thin steel plate is carried out to further study the fragment group expansion and projectile erosion of cylindrical projectile during hypervelocity impact on target plate. The empirical formula of perforation diameter of cylindrical projectile penetrating into target is given through the dimensional analysis method. The moving image of fragments behind the target is obtained by using high-speed camera，and the expansion law of fragment group and the erosion law of projectile are analyzed. The melting problems of projectile and target materials in hypervelocity impact is explored by analyzing the microstructure. It can be known from fitted experimental data that the perforation diameter of target plate，the maximum axial expansion velocity and maximum transverse expansion velocity of fragments are approximately related to the diameter of projectile，the thickness of target plate， and the impact velocity，and the projectile erosion length is also related to the projectile length-to-diameter ratio in addition to the above parameters. In the hypervelocity impact of cylindrical projectile on target plate，spallation occurs on the back surface of target plate，and a ‘tip’ of velocity greater than the velocity of remaining projectile is formed in the front of the fragment group，which can be approximately determined by the thickness of target plate being less than 0.72 times of projectile diameter. When the 93 tungsten cylindrical projectile impacts the steel target at the speed of 2-3 km/s，the fragment group behind the target is not melted in a large range，but when the fragments and the remaining projectile impact the second layer of target plate，the material near the impact zone melts in a large range.

Key words: cylindrical93tungstenprojectile, hypervelocityimpact, thinsteelplate, perforationdiameter, fragmentgroupexpansion, projectileerosion, materialmelting