Aiming at the technical risk assessment in the development stage of the equipment, based on the cloud model theory, the qualitative knowledge rules between the induction and evaluation index and the technical risk are summarized, and the mapping agent of the key technology risk index is designed based on the knowledge rule set, got the non-linear mapping relationship between technical risk index and the technical risk, established technical risk probability and influence assessment model. Through the model, the risk probability and influence of the key technology are evaluated, and it is found that there is a difference between the probability value and the influence value of the same risk, and the necessity of discussing and evaluating the risk probability and influence separately is explained. The research results show that the model realizes the quantization evaluation of technical risk probability and influence, and it can guides the equipment development technology risk prevention and treatment.