With different doping levels of Yb3+ in the Yb:YAG crystal, an efficient room-temperature Yb:YAG thin chip laser operating at 1.053 μm pumped by a Ti:sapphire laser was realized. For a 20 at-% Yb:YAG thin chip (6 mm×6 mm×0.5 mm), a 356 mW output power was obtained for an absorbed pump power of 784 mW, and an output coupler transmittivity of 4.26%, giving a slope efficiency of as high as 69% and an extrapolated threshold of 275 mW. The experimental set-up of the thin chip laser is described.