To eliminate the inaccuracy of engineering design

using a space narrow method in the conceptual design phase

further narrowed the scope of the design space.Preference structure was used to express a given design variable space and performance space preference variable.Quantitative relationship showed design variable space.The range of communication design space to performance space mapping was calculated with the interval propagation theorem.The design solution range met the changing needs of the performance was found.Unfeasible sub-space and uncertain factors was eliminated.Wet multi-disc brakes with the concept of design as an example that the method is correct

it is suitable for multi-objective design system.