A mathematic algorithm based on the adaptive fuzzy PID was introduced to monitor and regulate the nonlinear micro-pressure feature of inductively coupled plasma (ICP) vacuum chamber in the process of current patterned dry-etching of sapphire substrate. This algorithm realizes the regulation of micro-pressure of chamber in the vacuum condition flexibly through adjusting variables of the Mass Quality Flowmeter (MFC) and compression release valve connected with vacuum pump. The results of Matlab simulation and test on the dry-etching chamber substantiate the efficacy of this algorithm. In the vacuum condition ranged from 0.13 Pa to 20 Pa, the algorithm features strong robustness, small overshoot, short transition time, and etc. which can meet the dry-etching specification of standard etching rate, etching ration selectively and etching uniformity.