Abstract: For uranium materials shielded by the high Z matters, a new method was proposed to estimate their enrichments. Firstly, uranium materials and shieldings were irradiated by 14 MeV neutrons of a D-T neutron generator, and fission neutron/gamma time correlation spectra were obtained by fission radiation detectors at the same time. Secondly, geometry and material parameters were acquired by the tomographic images from imaging detectors. Monte Carlo simulations of different uranium enrichments were conducted with these parameters, and so simulation spectra of time correlation were got. Lastly, the actual uranium enrichments were fixed by searching the simulation spectra that match the measurement spectra. By analyzing all fission neutron/gamma time correlation spectra measured by fission radiation detectors, it is shown that the time correlation spectra of high-enriched uranium and depleted uranium are obviously different under each shielding condition. Thus, time correlation spectra can be a key technical feature to distinguish different enrichments of uranium materials. For uranium materials with the same enrichment and shielding, the simulation results coincide with the measurement results. So simulation and measurement analysis of the time correlation spectra can build technical basis for enrichment estimation of the uranium materials.