Neutron imaging techniques were investigated at Peking University based on a 4.5 MV Van de Graaff accelerator. The thermal neutron radiography, fast neutron radiography and fast neutron resonance radiography were tested. The low neutron flux limits the image quality. A new radio frequency quadrupole (RFQ) accelerator based on neutron source with a yield of 1 012 n/s is being set up.