A method is presented for constructing composite perfect hashing functions for letter-oriented key sets. Contrary to the usual perfect hashing, ours can store a large set of keys. Our scheme is inspired by Chang, Chen and Jan's method. With the help of a hashing indicator directory (HID), we compose a set of perfect hashing functions constructed by Chang, Chen and Jan's method. An algorithm to construct HIDs and a simple algorithm to retrieve data are also presented.