Abstract: It’s very important to choose observation well position in pumping test. Practically at present, the observation well position is chosen qualitatively only, but lack reliability and rationality. In the paper, the observation well position is optimized through establishing fuzzy decision model with multi-object and multilayer system. Three major factors are considered synthetically in the optimizing work, including the acute angle degree between the groundwater flow line and the connection line of the observation well and pumping well, hydrogeological factors, and the distance between the observation well and pumping well; and hydrogeological factors include three sub-factors, burial depth of the aquifer, thickness of the aquifer and the lithology. And then, the model is verified with pumping experiment data in the water source site at the Yishan fault zone along Xilong River. The results prove that the choice analysis can be turn to quantitative decision from the former qualitative description if the method in the paper is adopted, which can avoid subjective deviation, benefit to decision and make the conclusion being reliable.