To improve the emergency preparedness and response capabilities of spent fuel reprocessing nuclear accidents，a spent fuel reprocessing nuclear accident emergency scenario based on knowledge meta was proposed to address the uncertainty of the nuclear accident emergency evolution process，the importance of scenario analysis in emergency response decision-making，the complexity of the evolution process，and the difficulty of organization and implementation. The disaster event，causative agent，causal agent，and emergency response were determined，and then a dynamic scenario model for spent fuel reprocessing nuclear emergencies based on a DBN was developed to calculate the occurrence probability of key scenarios，evaluate the development trend of the scenarios，and analyze the evolution laws and paths. Taking the explosion of the high-release liquid storage tank of the Mayak spent fuel reprocessing plant as an example，the process of deduction of the scenario analysis method of the spent fuel reprocessing nuclear accident based on the knowledge meta theory and DBN was performed，and the results were further analyzed. The results showed that: the loss probability of emergency cooling water supply was 73%，the probability of explosion of the high-release waste liquid storage tank was 86%，the probability of radioactive nuclides transferred to animal and plant products and drinking water through multiple pathways was 87%，the probability of long-lived radioactive nuclides deposition in part of the area was 89%，and the probability of the event calming down and dying out was 72%. The probability of the accident contaminating the air，soil，and river was 89%，85%，and 81%，respectively. The probability of affecting public health and safety was 86%. The scenario evolution process is consistent with the emergency response development of the reprocessing storage tank explosion accident and its impact on the public and the environment，validating the model performance.