Yb3+:KGd(WO4)2 laser is a new solid-state laser source which has been paid much attention in the recent years. It is characterized with the high absorption and emission cross-section, broad fluorescent linewidth and low laser threshold. The microcosmic kinetic of three energy-level laser system is theoretically analyzed. After investigating the absorptive and emission features with the different crystal cuttings, pump and laser polarization directions, the relationship between the output characteristics of a Yb3+:KGd(WO4)2 laser and the crystal length as well as the reflectance of the output coupler is analyzed. Finally, the optimum conditions for a real Yb3+:KGd(WO4)2 laser have been obtained as: crystal cut-direction parallel to g axis, pump polarization direction parallel to m axis and laser polarization direction parallel to p axis.