The lower first member of Shahejie Formation (Sha 1 Submember) in the Qijiawu area in Huahua depression is dominated by carbonate reservoirs. Lithochemical analysis of 10 cores, carbon and oxygen isotopic and trace element compositions show that the content of SiO2, AI2O3 and CaO are relatively high,while the content of MgO varies with the difference of lithology. SiO2 is positively correlated with AI2O3, so SiO2 and K2O + Na2O, but is negatively associated with the MgO, indicating that SiO2 enrichment is subject to terrestrial material source and pH value of water in lake basin. With linearly increasing of Al2O3 and K2O+Na2O, increasing MgO is against SiO2 enrichment. Most of C and O isotopic Zvalue in each layer are higher than 120, indicating that frequent marine transgression resulted in salinization of water in which lacustrine carbonatic rock deposited. Decreasing δ18O value shows that CO2 and CO contained in hydrothermal fluid migrating along fault during deposition of Sha1 submember in the study resulted in further depletion of δ18O value in lacustrine carbonatic rock due to fractionation under the high temperature and pressure. The reason for relatively high contents of metals (such as Cu, Pb, Zn, Cr, Ni, and Ga) in various carbonatic rocks is related to frequent marine transgression and strong reduction environment, while change of Sr, Ba and B are restrained by addition of terrestrial material and ancient weather condition. Detailed studies of petrochemical composition, C and O isotopic analysis, and trace elements contents establish the geochemical basis for reconstructing ancient geographical environment of Sha 1 submember rock facies and predicting favorable reserves zones in the studying area.