Fixed abrasive diamond wire saw is widely used for slicing crystal quartz to manufacture new piezoelectric dynamometers. However, the process has always the problem of slicing out-of-straight influencing the dynamometer.s indicators, the optimization methods of machining and slicing process are studied in the paper. Developments of fixed abrasive diamond wire machining are reviewed firstly. A research system is built to monitor process and measure cutting forces. The 3-axis forces and their relationship with tension-force are investigated by measured curve. Force analysis of diamond wire at changing direction is shown in the experiment and the rule of slicing straight is found. Finally, suggestions on slicing parameters and methods are put forward.