Two kinds of improvement, ST improvement and ST-input-output improvement, on Yang-Gu algorithm have been proposed to design diffractive optical elements (DOE) used for beam shaping in this paper. These kinds of improvement can provide less sensitivity to the initial phases, better shaping quality, and higher iterative convergence efficiency. The validity of the two kinds of improvement is proved mathematically, and is shown by simulation of the practical design. Further, the ST-input-output improvement can mitigate the contradiction among the different parameters in beam shaping.