A method for controlling release amount of detergent and a washing device, include: dividing inner space of a detergent box into independent N compartments, wherein each of the compartments is configured to store a type of detergent having a certain concentration range; assigning a concentration level Ci, i=1, . . . , N to each of the compartments wherein the higher the detergent concentration, the lower the concentration level; selecting one of the compartments containing detergent and releasing the detergent in the selected compartment, and obtaining the concentration level C of the selected compartment; obtaining a laundry weight m; and calculating a release amount of the detergent, wherein Vn=1.25*m*(C+1). The formula which is configured to calculate the release amount of detergent is also provided based on both of the detergent concentration level and the laundry weight. Hence, the problem of excess foaming and residue caused by putting too much concentrated detergents which have to introduce more rinsing cycles could be effectively solved.