A genetic framework to optimize the dithering binary pattern in the phase domain was proposed, which searches a best binary patch instead of the whole pattern to handle the time-consuming difficulty of genetic algorithm. Experimental results show that the proposed technique can significantly improve the dithering fringe quality and it is robust to different amounts of defocusing. The phase root mean square error reduces from 1.493, 1.209, 0.989 rad to 0.972, 0.749, 0.603 rad respectively, when the projector is mildly defocused, moderately defoucsed, and severely defocused.