Aiming at the applicability of steel sheet pile cofferdam and earth rock cofferdam in specific environment and conditions，combined with the engineering boundary conditions，we study the applicability of cofferdam scheme，convenience of material source，engineering quality risk，construction period and construction cost. Based on comparison，we come to the conclusion that under the working conditions of tight construction period，high quality requirements and large upstream water head difference，the earth rock cofferdam has the advantages of better anti-seepage effect and lower cost，and is more suitable for the phase III cofferdam project of Qianwei navigation-power junction in Minjiang River. Based on the research and engineering practice，the key and difficult points of earth rock cofferdam construction and the technical measures and results are put forward，which may serve as reference for similar projects.