Abstract: In order to study the shape of the extreme ultraviolet(EUV) collector mirror and liquid droplets drift of the EUV light source system,the parameters for the collector mirror were calculated.The images of the intermediate focus were simulated with ZEMAX when the liquid droplets drifted 50μm,100μm,150μm from top to bottom and from left to right.The results show that the drift of the liquid micro-droplets in the upper and the lower direction have great influence on the imaging of the intermediate focus point,the drift should be controlled below 20μm in this direction,and the drift of the liquid micro-droplets in the optical axis direction have smaller influence on the imaging of the intermediate focus point.