Based on integrated study, the paper discussed the structural characteristics of the weathered crust on top of Pre-Tertiary in the Jiyang depression. Key factors controlling its formation, structural model of the weathered crust and its influence on the reservoir formation were also discussed. The research showed that weathered clay layer in the studied weathered crust is thin with limited distribution, suggesting a poor reservoir property；while semi-weathered rock of various lithologies extensively developed in the whole area, except for the tight "crust" on the top of semi-weathered carbonate stone, reservoir property was improved obviously. Structure of weathered crust is controlled by lithofacies, paleoclimate, weathering time, paleotopography, and sedimentary environment of the overlying strata. All these factors determine spatial distribution of the structure of weathered crust. The weathered clay layer and "crust" on the top of semi-weathered rock serves as caprock for petroleum reservoir, while semi-weathered rock without “crust” can improve reservoir property of Tertiary system and serve as lateral migration path between different strata.