There is a concealed red basin in northwestern Jiangxi, which is overlain by Quaternary sediments 30～50 m in thickness and underlain by Tertiary red sandstone. The water-prospecting work is very difficult in that area. Using soil absorbed mercury measurement and direct current IP method, the author analyzed and summed up the mode of occurrence of underground water in that area, detected water-prospecting orientation and optimized favorable ore-searching sectors, which yielded excellent result. Now this area has become a medium-size underground water source, with daily water production of over 30 000 tons. It is thus concluded that the combination of geophysical and geochemical methods is an effective means in search for underground water. Such a means is characterized by cheapness, rapidness, easy operation and high penetrating capacity in thick overburden areas, thus having extensive application vista.