Abstract: To investigate the variation of electron temperature of plasma generated by hypervelocity impact at close impact velocities and different incidence angles,a sweep Langmuir probe diagnostic system suitable for transient plasma diagnosis is designed.LY12 aluminum spherical projectiles are loaded by two stage light gas gun,using sweep Langmuir probe diagnostic system designed to measure plasma.The LY12 aluminum projectile impacted the LY12 aluminum target at incidence angles of 45°,60° and 90° in a horizontal plane.Effective data obtaied from experiments at positions of probes as given in every half period.The dependence of electron temperature on impact angles during the whole physical process were obtained.