This paper reports a laser diode (LD) end-pumped Yb∶YAG slab dual-wavelength laser amplifier with high power working at room temperature. The dual-wavelength stably operates at 1029.6, 1031.5 nm. Based on the broadband fluorescence characteristic of Yb∶YAG, the dual-wavelength amplification model is built and corresponding numerical simulation is taken to study the laser spectrum amplification output properties under different pump conditions. 940 nm laser diodes is used to pump the Yb∶YAG crystal at two ends. The seed laser with the dual-wavelength spectrum is injected from one end of the crystal and amplified. Experimental results show that continuous-wave (CW) dual-wavelength laser output power of 6.56 kW is acquired when the seed injection is 1.18 kW, which matches the simulation results. These theoretical and experimental researches of dual-wavelength laser amplification can lay the foundation for the applications such as high-power spectral combination, etc.