An improved space-time conservation element and solution element (CE/SE) scheme is used to simulate propagation process of 3-D oxy-hydrogen detonation in rectangular tubes. Multiple detonation structure based on elementary cells of the diagonal, rectangular and spinning mode in square tubes are obtained by numerical cases with different aspect ratios of cross-section. By means of visualizing its detailed structure, the formation mechanism of 3-D multiple cellular patterns is preliminarily discussed. As the cross-sectional aspect ratio increases, new multiple cellular patterns are observed.