In the northwest margin of Junggar Basin Wuerhe, two sets of reservoirs including the dolomitic rock and the volcanic rock are developed in Permian Fengcheng Formation. An analysis of the distribution range of the dolomitic rock reservoir is very important for the petroleum exploration in the study area. However, these two rocks have the same seismic reflection, so they cannot be distinguished only by using the amplitude data. In this paper, the spectral decomposition is used to analyze the difference between the dolomitic rock and the volcanic rock so as to distinguish their distribution range. Then according to the actual well test data, the relations between the deliverability of the reservoir and the spectral parameters are obtained. Based on the relations, the spectral property is extracted to predict the distribution range of the high quality dolomitic rock reservoir, to provide a technology support for the exploration of Permian Fengcheng Formation in this area. The method of using spectral decomposition to predict the high quality dolomitic rock reservoir can also be used for studying the dolomitic rock in other areas.