An innovative laser amplifier architecture based on cryogenically cooled Yb∶YAG bulk is developed for high-power laser application. The Yb∶YAG bulk with triangular-section channels on the side is cooled using a cryogenic liquid to suppress parasitic oscillation in the medium and improve heat management. This architecture realizes high-efficiency energy storage and extraction of the amplifier, and a laser output with energy of 9.4 J, pulse width of 10 ns, repetition frequency of 5 Hz, diffraction limit far field of 3.3 is obtained, when high energy storage and extraction efficiency of the amplifier are realized. It provides a useful reference for the subsequent design of Yb∶YAG laser amplifier with large energy.