With 20—45 MeV O5+ ion bombardment we investigate L-shell X-ray emission processes on Ta film at HI-13 tandem accelerator in the Chinese Institute of Atomic Energy (CIAE). The ratios of X-ray emission cross section: σ(Lβ)/σ(Lα),σ(Lγ)/σ(Lα), and σ(Ll)/σ(Lα) are obtained. The results are compared with the predictions by the ECPSSR theory. Reasonable agreement between the ECPSSR theory and the experiment is obtained.