Iterative algorithm based on fuzzy control theory (IAFC) is put forward for designing diffractive optical elements for laser beam shaping, aiming at decreasing both mean square error and top beam uniformity of the output beam. Derived from Gercherg-Saxton (G-S) algorithm, the profile-smoothing algorithm is put forward, which can effectively improve the uniformity of top beam, but has a poor performance at the mean square error. Combining the profile-smoothing algorithm and the Gercherg-Saxton algorithm by fuzzy control theory, the iterative algorithm based on fuzzy control theory, can decrease both mean square error and uniformity of beam top. Computer-designed result by using the iterative algorithm based on fuzzy control theory leads to an excellent output beam, and the mean square error and top beam uniformity of beam are 0.75% and 0.46% respectively, while the energy conversion efficiency is up to 94.91%.