Principle of maximum entropy(POME) is a method for estimating the parameters of probability distribution.The paper discussed the method that used the maximum entropy principle to infer the mathematical properties of estimation parameters of probability distribution of POME.The relationships between POME and Mellin transform were analyzed. From Mellin transform,it derived POME of estimation parameters of 13 kinds of hydrological frequency distribution curve and illustrated the specific steps of derivation. The process of inferring POME by Mellin transform is simpler and easier to be understood.