The etching process of the high aspect ratio of silicon deep trench is the key technology in MEMS field.Having used Oxford Plasmalabsystem100 ICP-180 etcher and with SF6 and C4F8 as the etching gas,it has studied the influence on the deep silicon etching process of Bosch under different ICP power,bias voltage,temperature,pressure and other parameters.The experimental result shows that under appropriate parameters,the high aspect ratio of silicon deep trench is greater than 26:1,the sidewalls' vertical degree is 89.9? And the etching rate is greater than 2μm/min; the high aspect ratio of SOI deep trench is greater than 33:1,the sidewalls' vertical degree is 89.7? And the etching rate is greater than 2μm/min.