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In this study, the effects of bundle geometries and initial pressures on the detonation transmission behaviors were examined systematically in a circular tube with 6 m long and an inner diameter of 90 mm. The tube bundle structures were created by inserting several smaller pipes (20 mm outer diameter, 2 mm wall thickness) into the tube. Three different bundle structures can be obtained by varying the number of smaller pipes n of 3, 4 and 5. The iron probes and pressure transducers were used to determine the average velocity while the smoked foil technique was adopted to register the detonation cellular structures. The experimental results indicate that detonation can propagate at about the theoretical CJ velocity when the initial pressure (P0) is greater than the critical value (Pc). However, when the initial pressure approaches to the critical value, the average velocity is decayed rapidly causing the failure of detonation. For the cases of n = 3 and 4, the phenomenon of detonation re-initiation with clear cellular pattern can be observed. The re-initiation distance is increased remarkably at P0 ≈ Pc. In the case of n = 5, the detonation velocity experiences a more violent fluctuation, and the value of the critical pressure is increased to 28 kPa sharply. Finally, the critical condition analysis of successful transmission is performed. The critical condition can be quantified as DH/λ > 1. However, the critical values of DH/λ are not uniform among various tube bundles, but in a small range, i.e., from 1.78 to 2.35.