Abstract: Significant scale effect exists in rock strength and deformation.In this paper, the origin, variation law and influencing factors of scale effect of rock strength and deformation in petroleum engineering are summarized and analyzed, and suggestions for future research are given.The results show that:heterogeneity theory and end friction effect theory are the main theories to explain the origin of scale effect of rock strength and deformation, but the strength and deformation of actual rock are bound to be constrained by both of them.The difference is that the dominant factors are different for rock samples of different scales.At present, the influence of scale change on strength and deformation of rock samples is still full of divergence, and the universality of prediction models needs to be improved.10 factors, such as rock type and heterogeneity, all affect the scale effect law of rock strength and deformation; 6 directions, such as setting up unified testing and evaluation standards in the industry and carrying out the scale effect experiment of rock strength and deformation under reservoir conditions, are the research focus of scale effect of rock strength and deformation in petroleum engineering in the future.The study of scale effect of rock strength and deformation has the important guiding significance for drilling safety and fracturing design.