For the soft mattress laying in Hechangzhou Section of 12.5 m deepwater channel regulation project of the Yangtze River below Nanjing,the deepest mud surface elevation is -42.9 m,the actual measure flow velocity is 2.1 ms,and the longest completed length is over 640 m.In order to solve the problem of laying and controlling of long soft platoon in deep water and large flow rate condition,we use the whole process quality control technology to control the whole process before and after laying.The width of the lap and the overall quality meet the design requirements.