The invention discloses a method for treating flushing water in polyvinyl chloride paste resin production. The flushing water from a polymerization procedure sequentially flows through a homogenization tank, a sedimentation tank, a quick mixing tank, a slow mixing tank, an air floatation separation tank, a continuous sand filter tank and a clean water tank, and finally enters a mother solution water treatment system; sludge generated in the whole process enters a sludge tank, and sludge cakes generated after the sludge is dehydrated through a plate-and-frame filter press are recycled and sold outwards. The flushing water in the paste resin production is subjected to solid-liquid separation through the methods of chemical sedimentation and air floatation separation, so that the dosing quantity is greatly reduced, the production cost is reduced, the benefits are increased, the burden of mother solution water treatment is reduced, and the environmental pollution is reduced.