Abstract: Taking the 12 kV/1250 A/31.5 kA vacuum interrupter as the research object, an uncertainty optimization model for the magnetic field characteristics of the interrupter contact structure is established by using an interval optimization method that takes into account tolerance design. Taking slot length of contact blade, chute depth of contact, deflection angle of the slot on the contact blade and contact cup holder thickness as optimization variables, the interval is used to describe the preparation and measurement errors of the design parameters, and tolerance indicators and interval possibility models are introduced to transform this uncertain optimization model into a deterministic optimization model. The NSGA-Ⅱ(Non-dominated Sorting Genetic Algorithm-Ⅱ) algorithm is used to obtain the set of non-dominated solutions of the Pareto front with the objective of maximizing both the maximum magnetic induction intensity in the central plane between poles and the design tolerance index, and optimal design parameters are obtained, and the optimal design of the internal magnetic field of the interrupter considering the influence of tolerance is realized.