Abstract: Due to strong heterogeneity, various reservoir spaces and types as well as complicated formation structure and combination, it is difficult to evaluate reservoir and divide effective pay thickness for reservoir calculation in carbonate reservoir. Based on analyses of reservoir types and rock-electricity characteristics of carbonate buried-hill in the Jiyang Depression, using normal well-logging and imaging as well as nuclear magnetic logging technology, we qualitatively identified and quantitatively interpreted fracture, cave and pore. The effect of fracture, cave and pore was judged, and the division standard for effective pay thickness was established. A set of evaluation method suitable for the effective pay thickness of carbonate buried hill reservoir in the Jiyang Depression was put forward. Taking into consideration of the particularity and the drilling features of carbonate buried hill reservoir, a method for selecting effective pay thickness of reservoir unit was proposed.