Dry strength agent can be widely used in papermaking of packaging paper, household paper, newsprint, cultural paper and other paper. It can effectively improve the paper folding strength, bursting strength, stiffness, ring crush strength and so on. On papermaking system with much anionic impurities or high electrolyte concentration, the effect is particularly evident. At the same time it has retention effect to flake fine and filler can reduce the loss of fibers and linting and dusting phenomenon. It can produce enough dry strength and allows the use of inexprensive fiber or a higher proportion of secondhand fiber.