A primary element and secondary element safety assessment method and system. The method includes the steps of: performing state evaluation on a primary element, determining the state level of the primary element, and determining the fault rate of the primary element according to the state level of the primary element; adopting a secondary element evaluation method corresponding to a risk assessment type to determine associated secondary elements, performing state evaluation on each secondary element, and obtaining the state evaluation level of each secondary element; according to the state evaluation level of each secondary element and a preset secondary element fault rate determination method, determining the failure probability, the false action probability and action rejection probability of the primary element due to stopping, false action and action rejection of the secondary elements; and determining the total failure rate of the primary element corresponding to the risk assessment type according to the fault rate, failure probability, false action probability and action rejection probability of the primary element. Based on the scheme of the method provided by the embodiment of the invention, the overall risk of operation of the primary element can be assessed comprehensively, and the degree of accuracy of a safety assessment result is improved.