Garnet type electrolyte is of particular interest due to its outstanding stability against Li metal and high ionic conductivity at room temperature. But insufficient solid to solid contact hinders its further application on solid state batteries. Herein, we demonstrate a strategy to deal with the large impedance of Li/Garnet interface by introducing LiAg alloy reaction at the interface. Due to the lithiophilic nature of Ag interlayer, intimate contact of the interface successfully reduces the area specific resistance of Li/Garnet from 1534 Ωcm2 to 66 Ωcm2. Li dendrite is also suppressed not only at the Li/Garnet interface but among the Garnet grain boundary due to the moderate Li flux environment. Hybrid solid state Li/Garnet/LiMn2O4 full cell with remarkable electrochemical properties is achieved. The hybrid solid state batteries with a “breathing” Li/Garnet interface helps better understand the interface behavior of the Li/Garnet and provides more inspirations to further realize solid state batteries with high energy and power density.