The invention discloses a multi-branch scheduling and switching mixed optimizing method in the polypropylene production process. According to the method, an auxiliary system track optimizing model and a main system scheduling sequence optimizing module for multi-brand switching in the double-ring-pipe technology polypropylene production process are established, a main system model and an auxiliary system model are optimized through a double-layer hierarchical mixed integer iteration dynamic optimizing method, wherein multi-brand switching operation tracks are optimized based on a control vector parameterization method, and a multi-brand switching and scheduling sequence is solved based on a CPLEX mixed integer optimizer. The mixed optimizing method can reduce the optimizing scale, total multi-brand switching time and total consumption of transition material. The optimal scheduling sequence of polypropylene multi-brand production and the optimal track of operation variable and product performance index changes in the switching process of all brands are searched for to instruct production, so that production of a polypropylene enterprise meets market requirements flexibly, and besides it is guaranteed that a polypropylene production device achieves maximum economical benefits with the minimum energy consumption and material consumption.