Abstract: Accident source terms used to evaluate the postulate accident radiological consequence closes relate to the core inventory. The results of core inventory calculation codes, such as ORIGEN, include hundreds of isotopes, even more. So how to select significant isotopes among large amounts of original data seems particularly important for conveniently and precisely assessing radiological consequence. By tracking the isotopes transportation to environment, the dose contribution of each isotope was calculated. The results show that only 30-50 isotopes can bound 95% contributions to dose consequence, these isotopes can be the base of radiological consequence calculation and core inventory source terms selection. The method mentioned may provide a reference to review the general postulate accident radiological consequence.