With the continuous improvement of the industrialization level, the measurement of large-size parts based on machine vision has been hot in research. Firstly, this paper explains the research background of machine vision measurement technology and the current research status at home and abroad, points out the difficulties of current vision measurement research, advocates to improve measurement accuracy and efficiency by studying image processing algorithms. Secondly, this paper researches the edge detection technology, which mainly uses the coarse and fine positioning edge detection algorithm in vision measurement. Sub-pixel edge detection algorithms in precise edge positioning are highlighted for analysis. Then, the image stitching techniques used in the measurement of large size parts are investigated and analyzed. The image registration applied by this technology is mainly based on two types of methods: region and feature. This paper also analyzes the advantages and disadvantages of these two types of methods. Finally, the characteristics and limitations of the measurement methods for large size parts are summarized, and future further exploring directions for improvement are pointed out.