Shahejie Formation reservoir in Qikou 18-1 Block belongs to fan delta facies, with rapidly changed sand body, and the sparse well data in the block is not enough for the reservoir study of high accuracy. On the basis of lithologic calibration with well data, optimum selecting seismic attributes extracted from 3D seismic data, especially RMS, is able to discriminate the thick sandstone from the mudstone, and as a result, the scope of fan delta, which is the favorable sedimentary facies of the block, can be determined with the sandstone distribution. Practically, it is proved that this set of reservoir prediction technology is comparatively fit for determination of favorable target in offshore oilfield with sparse well net and is useful for risk reduction in development.