One electron capture process and direct exciting process both occured in collision between-He+ and Ar in energy range 70-150 keV. From the comparison of experimental results between He++Ar and He++Ne collision systems, we see that the emission cross sections of the triplet Hel of the former are much larger than those of the latter, when the velocity of incident ion He+ is small. The latter become larger than the former, when the velocity of He+ is greater than 1.0 a.u (2.2×108 cm/s). Therefore, the potential energy defect and the velocity of projectile are very important factors in the electron capture process and there is a competition between them-in collisions.