Target ionization accompanied with projectile electron loss is investigated for 0.2-7 MeV Cq+ (q = 1-4) with He and 0.25-5 MeV Oq+ (q = 1-4) with He collisions. For projectile single-electron loss channel, the He double-to-single ionization ratio R is nearly independent of projectile charge state but dependent on the nuclear charge of projectile Zp. The results are analysed with atomic structure qualitatively. So far there have not existed the experimental data comparable with our results, to our knowledge. The ratio -R is interpreted in terms of the two-step mechanism. This analysis agrees well with similar experiments in the literature.