Abstract: Aiming at the problem that product configuration rules extraction method based on traditional rough set has poor noisetolerance capability, a variable precision rough set method was used to construct configuration decision table according to product design case data, to carry out relative attribute reduction based on decision class lower approximation and value reduction based on corevalue attributes through setting classification precision, and then acquire effective configuration rules based on support degree. Considering the effect of design case data addition on configuration rules extraction, an incremental updating method was proposed to update product configuration rules based on confidence degree, and to deal with the relationships of repetition, inclusion and confliction between newly added configuration rules and the original configuration rules. A case study of horizontal directional drilling configuration rules extraction was presented to illustrate the feasibility and effectiveness of the proposed method.