Digital image correlation method (DIC) can realize non-contact displacement measurement of member by spraying uniform speckle on member surface and taking pictures before and after deformation, which has been widely used in mechanical, aviation and other engineering fields. Considering the problems of poor recognition effect and low calculation efficiency in deformation measurement of traditional integral pixel algorithm for painted beams of ancient buildings caused by painted pattern uneven gray scale, Improve-Adaptive Rood Pattern Search (IARPS) method is proposed. Firstly, predict the search radius of the first search point and search exhaustively within the radius, and then Adaptive Rood Pattern Search was introduced to search the whole pixel displacement through small diamond search. By using simulated speckle pattern displacement and the bending test of common regular painted pattern decorative wood beam, IARPS is compared with the coarse-fine search method commonly used in DIC. Through comparative analysis, the results show that IARPS method overcomes the imprecision of local computation in the coarse-fine search method, the calculation efficiency can be improved by 71.6% and IARPS provides a new method to apply DIC to non-contact deformation measurement of ancient painted beams.