Abstract: On the basis of many tests and designs, an improved method for the hydraulic design of double-channel pumps was provided, and some main parameters of the impeller and volute by statistics and analysis were concluded. The methods for calculating radius R₁ of front cover board and radius R₂ of back cover board were presented. The midline equation of impeller plan channel was suggested in this paper for the first time. The calculation methods on the inlet diameter D₃ and width b₃, the tongue angel φ₀ and area F₃, and area ratio y were given. The research results have been applied to the product design of double-channel pumps.