The invention relates to an automatic simplifying and evaluating method of part model facing to steady-state thermal analysis, comprising the following steps of inputting an SAT form part model; identifying the transition features of the part model according to set transition feature threshold values, and inhibiting the transition features to generate a part model M with the transition features inhibited; setting fine feature threshold values and high curvature feature threshold values aiming at the part model M, performing a shape feature identification algorithm to identify the fine features and the high curvature features of the part model M, and establishing a feature linked list; computing the distance similarity of each feature by an ergodic feature linked list, and sequencing from high to low according to the distance similarity to establish an operational feature set; sequentially performing corresponding feather simplifying operation to generate a simplifying scheme set aiming at the operational feature set; selecting a proper simplified model from the simplifying scheme set, and computing model error equivalence ratio and time equivalence ratio to realize the evaluation of the simplified model and output the simplified model.