Abstract: Aimed to prove the capture efficiency of ion source injected Interdigital H mode (IH) cavity, a short linac is under construction in Institute of Fluid Physics, CAEP. Protons could be accelerated from 0.04 MeV to 2.4 MeV with this linac. The cavity was manufactured, cold test and cavity tuning were performed. After frequency tuning and field tuning, both frequency error and voltage distribution error were successfully decreased. Simulation results shows that capture efficiency of this cavity was increased from 16% to 34% by cavity tuning. The cavity parameters have reached the tuning objective and beam test will be carried out.