Horizontal zonality sequence of geochemical anomalies is traditionally determined by means of dimensions of anomalies or linear metal quantity contrast. The sequence thus obtained mainly reflectds anomaly intensities of different indicator elements instead of ordered spatial arrangement of anomaly centers, and hence fails to indiccate the complete relative reactivities of elements. The horizontal zonality sequence calculated by the center-of-gravity method can not only reflect spatial variation regularity of different indicator elements realtive to the mineralization center under the ore-forming and halo-forming action, but also indicate effectively relative reactivities of elements in the ore-forming and halo-forming process. The center-of-gravity method has unequivocal mathematic and geochemical implications and also applies to the calculation of ordered arrangement of vertical zones.