The invention provides a clothes size recommendation method and system. The problem that sizes of clothes sellers are not unified or accurate, so that a user who buys clothes on line cannot select the proper size is solved. The height and the BMI body type of the user are considered comprehensively, the proper number type is determined first, the corresponding size is found, then the size is adjusted to fit the body type of the user, the adjusted size is recommended to the user, so that trouble of size selecting is avoided for the user, and particularly the trouble in the situation that the size of the selected clothes does not accord with the mainstream size standard is avoided. According to the method and system, only the height and the weight of the user are used, compared with a traditional method in which data such as the chest circumference, the waistline and the leg length are used, operation is simplified, complexity is lowered, the size is determined with the number type as the standard, the proper size can be accurately recommended, and the method and system are suitable for E-business sites where a larger number of sellers are located.