This paper presents a method of three-dimensional(3D) measurement based on double-hole defocused imaging.This method adds phase masks in the imaging light path to make the defocused object have double images on the CCD,and according to the double images′ relative positions,the object′s three-dimensional position is acquired.Based on analyzing the camera imaging model,the paper deduces the three-dimensional inversion model of defocused imaging.The influence of the structural parameters on the measurement accuracy is alalyzed,the three-dimensional measurement system is established,and the rack measurement experiment is performed.The results show that this method can realize fast and non-contact rack measurement,and gets high measuring accuracy.