Abstract: According the requirement of system injection in geothermal utilization,the temperature of the heat source at the exit of the system is specified and 5 kinds of organic working medium with different critical temperatures are selected for thermodynamic calculation. The heat distribution and the performance of DPORC with running time were studied,and the results indicated that the maximum value of the thermodynamic parameters of the system and the minimum value of the flow of organic working medium were obtained at the same k（Ratio of heat provided by the heat source to the high-pressure cycle to heat provided by the heat source to DPORC）value. The net output power of system with R600 and R245fa as working fluid is larger. Compared with R601,the net output power of system with R245fa as fluid can increase by 168.06 kW（5.55%）,while thermal efficiency and exergy efficiency can increase by 0.70% and 2.86% respectively. Compared with single-pressure organic（SPORC）,DPORC can reduce the decrease of net output power with variable running time effectively. After 40 a of operation,R601 has the lowest net output power reduction（428.11 kW,14.14%）,while R600 has the highest net output power reduction（526.75 k W,16.55%）.