A novel monolithic passively Q-switched microchip laser is presented with a microcavity by directly growing a thin Cr4+:YAG film with saturable absorption on the surface of the laser medium Nd3+:YAG by liquid phase epitaxy. Because of the homogeneous epitaxial process, a good interface property is achieved between active medium Nd3+:YAG and saturable absorber Cr4+:YAG. Pumped by 1 W output of a fiber-coupled laser diode, the novel laser produces Q-switched pulses sequence with wavelength 1.064 μm, pulse duration 1.8 ns, pulse repetition over 4 kHz, TEM00 mode and peak power nearly 1 kW. Except for the detailed descriptions of the performance of the laser, the potential advantages of the structure and relevant processes are also discussed.