A new real-time calibration method of dual dimensions size vision measuring system based on pixel equivalent is proposed to resolve the existing problems of thermal vacuum environment′s effect on vision measurement accuracy.This method makes use of standard component made of quartz material and carved with lines in known sizes as measuring base,and it can obtain real-time pixel equivalent value in high precision to reduce measurement error of environment by using first-order differential expectations of sub-pixel algorithm and least square fitting algorithm.Experiment results in thermal vacuum environment show that this method can be used in the calibration of dual dimensions small size vision measurement.