A control system and method of a semiconductor inspection system are disclosed, wherein the inspection can be conducted without reducing the reliability of measurement even in the case where the supply voltage drops. The control system has a controller, a power supply for a power on-off circuit constituting a switching regulator designed to maintain the output voltage against a supply voltage drop, and a supply voltage drop detector. In the case where a supply voltage drop is detected during the measurement, the measurement is automatically suspended, and after restoring the supply voltage, the measurement is automatically restarted.