Abstract: Turbine efficiency is generally assumed to be a constant value in the conventional organic Rankine cycle（ORC）. A turbine efficiency varies with the type of working fluids and the operating parameters. Therefore,a calculation model of the turbine efficiency is presented and the dynamic turbine efficiency is coupled with ORC system. The variation of the turbine efficiency with evaporation temperature and condensation temperature were analyzed,and thermal efficiency of ORC system with constant turbine efficiency and dynamic turbine efficiency were compared. Considering thermodynamic and economic performances,multi-objective algorithm was adopted to select the optimal working fluid and determine the operating parameters for constant turbine efficiency ORC system and dynamic turbine efficiency ORC system,and the optimal results were compared and analyzed. The results show that the turbine efficiency increases with the decrement of evaporation temperature or the increment of condensation temperature. Turbine efficiency is different for different working fluids and operating parameters,the maximum difference value is 0.148. There is significant difference of thermal efficiency between constant turbine efficiency ORC and dynamic turbine efficiency ORC,which is more obvious in high evaporation temperature range. For constant turbine efficiency ORC system,R245 ca and R236 ea are the optimal working fluids,while for dynamic turbine efficiency ORC system,R114 is the optimal working fluid. The optimal evaporation and condensation temperature changed a lot after the introduction of dynamic turbine efficiency.