Yb3+:KGd(WO4)2 crystal has been paid much attention in the recent years because of its broad gain bandwidth and high dopant concentration and it is considered as an ideal laser medium for constructing a mode-locked femtosecond or a radiation-balanced laser system. A quasi-three-level kinetic model has been built to carry out the theoretical analyses for both the seed part and the amplification part in a Yb3+:KGd(WO4)2 laser system with end-pumped configurations. The research first investigated the physical characteristics of the seed part based on analyses of the rate equations and found that the optimal crystal length and optimal output coupler reflectivity should exist in a lasing oscillator. Because the thermal conductivity of a Yb3+:KGd(WO4)2 crystal was relatively low, the research employed a master oscillator power-amplifier (MOPA) to realize the 30 W-output power. Finally, the output physical features of the MOPA part was analyzed. The research results are thought to be useful for construction of a practical Yb3+:KGd(WO4)2 laser system.