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在光束整形衍射光学元件的设计中，为提高目标衍射图样的重构精度，提出了一种基于相位混合的迭代算法。该算法采用复振幅每次迭代循环的初始相位与返回相位的加权和为驱动函数，并以每次循环开始和结束时的光强比较作为光束相位变换的判据。简单讨论了Gerchberg-Saxton(GS)算法的缺陷，并以高斯分布-均匀分布和高斯分布-环分布为例，对比了改进算法与GS算法的设计结果。计算机仿真结果表明，改进算法的极限收敛精度比GS算法高几个数量级，其能量利用率、顶部不均匀性等指标也均优于GS算法。该算法能获得重构精度较高的输出图样，对衍射光学元件的优化设计具体参考意义。“,”A modified iterative algorithm based on phase mixture was put forward in designing diffractive optical elements, aiming at recovering diffractive patterns of the output beam precisely. Different from Gerchberg-Saxton algorithm, in this paper, the new phase initiation was set as the weighted sum of the two phase functions in the succeeding neighbor loops to be immune from trapping local minimum. The formulas for calculating phase factor were given, and the selection of phase factor was discussed. The beam transformations from Gaussian distribution to uniform and to annular distribution were exampled to investigate with Gerchberg-Saxton algorithm and the proposed algorithm. The numerical result demonstrates a nearly uniform and annular target profile, and the ultimate mean square error, top beam uniformity, and energy efficiency of the proposed algorithm were all more excellent than Gerchberg-Saxton algorithm. This work can obtain better output diffraction pattern, and has reference value for the design of diffractive optical elements.