Abstract: This study analyze the response coefficient, theoretical apparent resistivity of different deep medium and the depth of probe based on 1-dimension model of electrical structure in Changli station. The results show that when MN is 1/3AB, 1/4AB, 1/5AB respectively, the variation trends of response coefficient of each layer are very consistent. Because the contribution rate of third layer which achieved 70 percent is highest in four layers of different depth, the contribution rate of the third layer is the dominant factor in arranging the electrodes for multi-spacing system in apparent resistivity observation. When the scale of electrode distance of the third layer is from 300 to 500 meters, the results are best. The third layer contribution rate is no more than 60%. When the electrode distance is less than 1000 meters, the contribution rate of the forth layer is just 20 percent. According to the distribution of the response coefficient of the deep layer and the actual observation conditions of the station, the multi-separation array layout is 5 kinds:AB=1 000 m, 500(or 400)m, 400(or 300)m, 125 m, 30 m, the detecting depths is around 14-96 m, the results rely on the electrical structure of medium under the Changli station.