Abstract: 4.5 MV Van de Graaff electrostatic accelerator at Peking University is running well in recent two years, and the applications mainly done are in the fields of neutron cross-section measurement, neutron radiography technique and research of radiation damage to different materials. The improvement of injection system has lift up ion beam transport efficiency increased the DC beam current obviously. Waveform of pulsed ion beams in different repetition rates was measured by neutron time of flight method after the extended progress in pulsing system circuits.