Abstract: According to the development of Model 9GSCC-1.4 water grass harvester, experimental studies on the cutting and pickingup unit and their arrangement for flexible sunken plant were carried out. The problems of breaking knives and winding with the plant around the knives were also studied. The first conclusion is that the reciprocating knife is found to be more suitable. The reciprocating knife, pickingup unit and conveyer are combined on the harvesting frame which has a certain angle of inclination. There are four forms on the arrangement between the reciprocating knife and the transport loading ship: (1) Place the harvesting frame in the front and set up the carrier chain after it. (2) Place the harvesting frame at the back of the ship and convey the plant to the loading ship immediately. (3) Place the door frame knife in the front without the pickingup unit and conveyer. (4) Place the knife on the side of the ship without the picking-up unit and conveyer. The second conclusion is according to the effect of the breaking knives and the inability of the equipment to pick up all of the plants, it is more appropriate to choose the chain board carrier which has many claws. The transporting velocity is higher than the whole ship's working speed. The speed radio is 1.4～1.6. The third conclusion is that the slope harvesting frame under water can prevent the flexible sunken plant from rolling. In general the limiting angle is 30°～45°. When we pick up or transport flexible sunken plant under water, all of the revolving shafts must be covered with the antiwinding units. This means that the revolving shaft must be installed in the speciallymade antiwinding shield.