Abstract: Detonation cell size reflects the characteristic of a given fuel mixture, which can be used to determine the critical values in various detonation phenomena, such as the critical diameter for the propagation in narrow, smooth wall-bounded tubes, the critical size for the detonation to survive diffraction from a tube into an unconfined space. However, measurement of the detonation cell size is highly subjective, especially for irregular mixtures. To reduce the uncertainty in manual observation, two methods are adopted in the present study to statistically analyze the detonation cell size in numerical simulations. The first method is based on the probability density function of the main track spacing between neighboring triple points moving in the same direction according to the vorticity records, and the second method uses the autocorrelation function to spectrally analyze the vorticity records. Detonation cells with different degrees of regularity are obtained by numerically solving the reactive Euler equations with different activation energies, Ea. For a low activation energy Ea = 15, the cell is regular and its size obtained by the two methods is consistent with each other. For a moderate activation energy Ea = 20, the cell becomes irregular and there is a small difference between the calculated cell sizes by the two methods. As the activation energy is further increased, for both Ea = 25 and Ea = 27, the temperature sensitivity of the reaction is greater and the cells are highly irregular. Moreover, transverse waves begin to merge, leading to a large deviation between the cell sizes obtained by the two methods. This is because that the spacing probability density function method assumes equal weights to all the tracks, while the autocorrelation function spectral method inherently weights the vorticity value and takes local correlations into consideration. Therefore, the detonation cell size obtained by the latter method is closer to the detonation characteristic of real combustible mixtures.