Fluid-rock interaction accompanied by inspissation of fluids can make significant effects on hydrocarbon formation. According to integrated data of rock section, test analysis, geostatistics, on the basis of study on water consumption of main mineral alteration during diagenetic stage, water consumption of sandstone reservoir of Paleogene during diagenetic stage in the Dongying sag is integrally evaluated. The results show that water consumption function is general phenomenon in the Dongying sag. Kaolinization of feldspar is mainly water consumption reaction. Average quantity of total water consumption is 38. 3 Gt. Since sandbody volume of deep sector is bigger, its water consumption quantity, especially in subsag, is great.