By means of drilling core and analysis data, as well as logging data and seismic data,the source rock and reservoir rock of the Lower Paleozoic in eastern Tarim Basin are comprehensively evaluated. It is indicated that, the source rock within the Lower Paleozoic from Cambrian to Ordovician is in high and over mature stage, therefore providing hydrocarbon in the form of oil-cracking gas. It is pointed out that the effective cracking gas-bearing targets are concentrated in the northern Gucheng area. The primary reservoir is in two forms as follows: The granular limestone with fracture and dissolution pores mainly distributed in the west platform edge of Gucheng and in the east Luoxi platform; The dolomite with dissolution pores mainly distributed in the platform of eastern Tarim Basin. Combined with the analysis of regional tectonic evolution history, it is proposed that the nose structure of Gucheng and its north-west area are the most favorable areas, and Yingdong structure belt and other uplifts in the sag are the secondary favorable areas.