The angular acceleration of a rotary shaft is one of the most important parameters for revolution which is widely employed in practical applications. The principles and approaches for measuring angular mechanism, acceleration were studied to find a feasible way to obtain the accurate and successive value of angular acceleration. A new type of data acquisition device with USB module was developed based on microcontroller AT09S8515 and USB interface controlling IC PDIUSBD12. It was convenient to test the width of rotary speed signal by using the unique function of the microcon-troller for automatically capturing the rising or falling edge of a square wave.