Considering the complexity and changeability of geology and prone to large unbalanced and sudden loads during shield excavation, the concept and evaluation index of compliance of shield propulsion system was proposed. The calculation model of compliance was established based on parameterization analysis of propulsion system, then the compliance of propulsion system was calculated taking a certain 3.2　m domestic shield prototype for example. Compliance of four different types of shield propulsion system， including speed regulation and overflow mode, reduced pressure combined with large grouping overflow mode, reduced pressure combined with tiny grouping overflow mode and reduced pressure combined with main oil way overflow mode， was calculated under Matlab/Simulink simulation environment. In order to verify the compliance effect of shield propulsion system, evaluation and analysis of the compliance effect were carried out based on the actual loads met in a certain domestic metro engineering. The calculation results of the compliance and the evaluation of compliance effect both indicated that big differences existed in compliance among these four typical shields under the same sudden load, and the compliance was related to relief component, grouping pattern, working parameters and pipe layout of propulsion system. Therefore, the compliance of propulsion hydraulic system can be regarded as an index weighing the capacity that shield sustaining external sudden load, providing the compliance design philosophy and optimization objective for the new generation shield propulsion system.