Abstract: Exhaust waste heat utilization system based on organic Rankine cycle（ORC） is promising in marine diesel engines. An experiment was conducted for an ORC exhaust waste heat utilization system to investigate the performance of the system under multiple engine loads. The system takes a 10 MW marine diesel engine exhaust as the heat source,perfluoropropane（R245fa） as the organic working fluid,and water as the intermediate heat transfer medium. The test results show that,as the engine load increases,the exhaust heat exchanger efficiency increases,hot water and R245fa flow rates increase,the pressure at the expander inlet increases,the superheat at the expander inlet decreases,the system efficiency,exergy efficiency and output power improve. Under the maximum system performance condition,the net output power is 263.05 k W,with the system efficiency of 9.38%and exergy efficiency of 27.52%,the isentropic efficiencies of the screw expander and the pump are 75.56% and 39.47%,respectively. This indicates that the system presents great performance. Ultimately,based on the test results,the contribution approaches 3% for the ORC exhaust waste heat utilization system to the energy efficiency design index（EEDI） of a 120 000 ton class bulk carrier,the annual fuel savings and payback period are around 1.418 2×106 CNY/a and 3.29 a,respectively.