The study is made up of 4 parts, which are organic facies, Secondary hydrocarbon generation mechanism, hydrocarbon generation history, and reservoir formation analyses. First, organic facies of hydrocarbon source rock are divided into B, B1 and D facies, i.e., the S1g belongs to B facies while P1q B1 facies. Second, secondary hydrocarbon generation model is made by hydrocarbon thermal simulation. Third, through basin modeling, hydrocarbon generation history is divided into 4 phases, which are Caledonian, Hercynian-Indonsinian, Yanshanian, Late Yanshanian-Himalayan. In the end, reservoir formation models are constructed in Baiju depression of Subei basin: one is upper reservoir formation model,the other is lower.