The geotextiles-laying vessel appeared “dragging anchor” during sinking of D-shaped soft mattress in Madang section for the 6 m depth channel regulation project in the section from Wuhan to Anqing of the Yangtze River main line due to deep water and large flow velocity. Some traditional measures，such as increasing the length of upstream anchor cable and dropping linking anchor were proved ineffective for solving the problem completely. Therefore，two construction schemes for increasing the mooring force were presented： scheme I is to add another geotextiles-laying vessel in the upstream of the working vessel，while scheme II is to replace the head beam of soft mattress with two concrete interlocking blocks so as to increase the friction force on the head of the soft mattress. This paper analyzes the mooring force and the stressed state of flexible mattress. The field tests indicate that the scheme II is feasible，but scheme I cannot solve the problem of “dragging anchor”due to multiple influential factors.