The invention discloses a mirror field dispatching system and method for a tower type solar thermal power generation system. The system comprises a receiver, a heliostat, a light spot imaging device, a light spot collection device, an image processing device and a mirror field control system for switching or regulating the single mirror state of the heliostat to control the whole mirror field. The method comprises the following steps of: correcting the heliostat successfully installed in the mirror field; verifying the corrected heliostat, judging whether the heliostat is verified or not, and seeking the sun by the verified heliostat; repeatedly correcting an unverified heliostat, and taking the heliostat continuously unverified many times as a fault heliostat, wherein the heliostat during sun seeking is needed to be regularly verified so as to solve the problem that the accuracy is lowered due to long term running of the heliostat. Through scientifically and reasonably dispatching the heliostat, correction, verification as well as fault detection and diagnosis of the heliostat are finished on the premise of ensuring the sun seeking efficiency of the mirror field to the maximum, and safe and efficient operation of the mirror field is ensured.