A 10 W and 355 nm Nd:YAG laser is used for the blind hole drilling experiment of a 4 layer flexible circuit board (FPC). The interaction mechanism with UV laser and copper and polyimide (PI) is analysised,and the etching depth of single pulse under certain conditions on polyimide and copper is simulated. The effects of the processing methods on the micro-drilling quality are investigated and analyzed. Finally,the optimization of process parameters are obtained,that firstly using the power of 3.9 W,the frequency of 80 kHz,then secondly using the power down to 1.4 W with other parameters unchanged. The recast layer roughness and the bottom surface roughness are 0.88966 μm and 1.063 μm respectively. The scanning electron microscope (SEM) photograph,the 3D profile of bottom surface and the 2D profile of section of the blind hole measured by surface profile measuring system are given.