A series of Schmid factor (SF) maps for different slip and twinning modes in Zirconium were systematically calculated and comprehensively illustrated as a function of the tensile angle between the applied stress and the c-axis together with the projective angle on the basal plane. The deformation modes include three groups of slip systems, i.e. basal, prismatic, pyramidal and slips and four groups of twinning systems, i.e.{10-12}, {11-21}, {11-22} and {10-11}. The “soft” and “hard” orientation zones were determined in terms of individual plastic deformation modes. A variant selection criterion for slip and twinning of Zirconium is proposed. The plastic deformation mechanisms are interpreted based on the Schmid factor maps in combination with the experimental data on the critical resolved shear stress (CRSS) for different deformation modes. The predicted plastic deformation mechanisms are consistent with the existing experimental results.