Results of a detailed study of the He2+/Hg system in the collision energy range from 2 eV to 1 keV are reported. In this energy range the ionization leads to formation of He+ and Hg2+ in its ground state and four lowest excited states arising from the 5d96s configuration. The ionization cross section has a maximum at about 25 eV and drops by about an order of magnitude between the maximum and 2eV, and also between the maximum and 400 eV. An analysis of the electron and ion energy spectra leads to the conclusion that the ionization mechanism is molecular: at large separations the system undergoes charge exchange, He2++Hg to He+*(n=2)+Hg+(2S12/), and at separation of about 5 a0 the system autoionizes from the three potential curves arising at smaller distances from the configuration He+*(n=2)+Hg+(2S12/). A potential curve model is proposed.