Abstract: The problem of combination between the new and existing concrete need to be solved in Danjiangkou dam heightening project. Simulation calculation and three- times site tests proved that the key- way on the jointing surface was crucial. It was necessary to set artificial key- way on the down- streamdamsurface in the pre- period project where there was not key groove in advance. By comparing with traditional construction methods, the slotting made use of high- power discal sawcutting combined with drilling static expansion was adopted. It gained prize from the supervisor, designer, owner and experts as it was economical and effective, worthy reference in similar projects.