The ZnO_1-xSe_x compound semiconductor had been grown by radical source MBE for the first time and we succeeded in obtaining its large bandgap bowing parameter of 12.7eV. During this research, some SIMS depth profile of Se concentration occurred to show the formation of compositional ordering ZnO_1-xSe_x layers. (Fig.1a) The period of ZnO_1-xSe_x natural compositional ordering decreases with increasing Se concentration. The relationship between the period of the ordered layers and the Se concentration is consistent with Ferguson's theory. (Fig.1b) The dynamics of the two-dimensional nature of the compositional alternations of ZnO_1-xSe_x can be explained by taking the surface dynamic process of growth kinetics into consideration.