In this study, detonation cell sizes of binary fuel blends of methane-hydrogen-oxygen mixtures with different compositions (i.e., CH4-2H(2)-3O(2), CH4-H-2-2.5O(2) and CH4-4H(2)-4O(2)) are experimentally measured. Good agreement is found between the experimental data and predictions based on the chemical length scales obtained from a detailed chemical kinetic model. The results show that detonation structure in methane-hydrogen-oxygen mixtures are irregular and detonation cell size (lambda) for CH4-H-2-2.5O(2) mixture is larger than CH4-2H(2)-3O(2) and CH4-4H(2)-4O(2) mixtures. A linear relationship is determined by: lambda = 34.62 Delta(I), through scaling the detonation cell size with the ZND induction zone length (Delta(I)) for metha ne-hydrogen-oxygen mixtures, and this scaling function is universal in CH4-H-2-O-2 mixtures at three compositions. (C) 2016 Elsevier Ltd. All rights reserved.