Objective To study the galactagogue effect of Maidang Rutong Granules on the lactation rats.Methods The milk volume,morphology of mammary gland,serum prolactin level and pituitary acidophil number in lactation rats and the growth improvement in suckling mice were observed after administrating various dosages of Maidang Rutong Granules to lactation rats by gastric gavage.Results Maidang Rutong Granules can promote the dilation and hyperplasia of acinus cavity and conduit in mammary gland,reduce the mammary interlobular fat connective tissue,significantly increase pituitary acidophil number and serum prolactin level,increase the milk volume of lactation rats and their offspring's body weight.Conclusion Maidang Rutong Granules exhibit significant galactagogue effect on lactation rats.