The invention discloses a filtering device for a water and fertilizer integrated irrigation apparatus. The filtering device for the water and fertilizer integrated irrigation apparatus includes a support, an outer barrel is mounted at the top of the support, a hydraulic cylinder is mounted in the center of the support, an ejector rod is mounted at the top of the hydraulic cylinder, a water outletis formed in the middle of the top of the outer barrel, a water inlet is formed in the middle of the bottom of the outer barrel, the water inlet is connected with a water inlet pipe with a valve, theejector rod penetrates through the water inlet and is inserted into the outer barrel, a first ejector block and a second ejector block are mounted on the ejector rod, the first ejector block is located above the second ejector block, a conical first metal filter screen is mounted at the top of the first ejector block, and is in sliding contact with the outer barrel, a first limiting block matchedwith the first metal filter screen is mounted at the inner side of the outer barrel, and a first filling space is formed between the first metal filter screen and the outer barrel. The defects in theprior art can be overcome, and the backwashing effect and applicability of the filtering device are improved.