The invention discloses a synergist for improving crop resistance and fertilizer absorption capacity. The synergist includes the following components by weight: 20-30 parts of an oyster shell powder, 20-30 parts of a water chestnut skin powder, 10-20 parts of a chinaberry bark powder, 10-20 parts of a magnetic material, 10-20 parts of an illite powder, 5-10 parts of a shiitake mushroom polysaccharide extract. The synergist can, on one hand, improve the resistance of crops, especially reducing the pests and diseases significantly, improving waterlogging and drought resistance; and, on the other hand, greatly reduce the use of fertilizers, especially nitrogen fertilizers, preventing soil compaction. It can also significantly increase the content of active polysaccharides, especially β-glucan in crops. In addition, the raw materials are readily available, the cost is low, and there are significant economic benefits.