When using resin for online water treatment, when the quality of the resin is poor (not strong enough), the water pressure disturbance is large (especially high pressure disturbance), and the resin cylinder wall is damaged, the resin will enter the entire water system. It will affect the normal operation of other equipment in the system, so it is necessary to install a resin trap. The resin trap is mainly to install a stainless steel wedge wire filter screen with a pore size much smaller than that of the resin on the water system pipeline near the outlet of the ion exchanger and other equipment equipped with resin, and has a flushing function. When the resin passes through, it can be intercepted and captured by the wedge wire filter screen. Simultaneously, flushing is automatically performed by front and rear differential pressure to discharge trapped resin out of the system.