To solve the problems of the great change of scouring and silting and the imprecise measurement of earthwork,we measure the earthwork accurately by the automatic measurement instrument,which is equipped in the trailing suction hopper dredger:Changjing No.6,in the 12.5 m deepwater phase-II project of the Yangtze River below Nanjing.We also discuss the principle of the measurement and summarize its applications