Abstract: On the basis of resource evaluation and favorable area evaluation, this paper established a set of classified evaluation criteria for shale reservoirs in the Wufeng-Longmaxi Formations in the southern Sichuan Basin. The criteria for effective reservoir identification include porosity (Φ) greater than 3%, gas saturation (Sg) higher than 30%, density of rock matrix (DEN) below 2.7 g/cm³, brittleness index (BI) over 40% and gas contents (Vt) higher than 1 m³/t. These criteria can distinguish the reservoirs and non-reservoirs. Based on the conception of geological and engineering integration, gas contents (Vt) has been selected to characterize the resource foundation of shale reservoirs, which is positively correlated with porosity and organic matter abundance. The brittleness index (BI) positively correlating with siliceous and carbonate contents has been selected to characterize the compressibility. Gas contents and brittleness index can comprehensively characterize the geological and engineering characteristics of reservoirs. Effective shale reservoirs have been further divided into three types: Type I with gas contents over 4 m³/t and brittleness index greater than 50%; Type II with gas contents lower than 4 m3/t or brittleness index less than 50%; Type III with gas contents from 1 m³/t to 4 m3/t and brittleness index between 40%-50%. Reservoirs in the Wufeng Formation and the low member of the Longmaxi Formation have a good quality which mainly consist of Types I and II and locally Type III. According to the criteria established in this paper, evaluations for reservoir quality of horizontal drillings have been conducted, and correlations between penetration rate of Type I reservoir, testing production and estimate ultimate recovery (EUR) are positive. Horizontal wells with drilling efficiency of Type I reservoir over 50% have probability of 92% for testing production over 15×104 m3/d and the corresponding EUR exceeding 8000×104 m³, meeting the requirements of economic development.