Abstract: The theme discuss distortion of active cooling copper mirror theoretically and experimantally. Thereby, a serious multilayer mirrors are designed. Among those, a mutilayer mirror with circular coolant channel is better. Its total distortion only 0.10μm, when the pssure of coolant is 0.13MPa, the absorbed laser power is 86.9W. It is about 1/40 of the distortion of the traditional active cooling mirror under the same conditions.