Abstract A four-tube two-phase gasoline/air valveless air-breathing pulse detonation engine (PDE) was designed and tested to investigate the operating characteristics of multi-tube air-breathing PDE. The PDE was operated at a maximum frequency of 30 Hz per tube with a total maximum frequency of 120 Hz. Four different firing patterns were successfully carried out: single tube firing, dual tubes firing simultaneously, three tubes firing simultaneously, and four tubes firing simultaneously. The synchronicity of the detonation waves and back-propagation pressure waves under multi-tube firing patterns were quantified and compared. The averaged peak pressure of back-propagation pressure waves in the air plenum chamber was discussed. The experimental results indicated that the four-tube PDE could be operated successfully under the four firing patterns and transform from one firing pattern to another. The time of arrival differences of detonation waves showed up in all multi-tubes firing patterns, which led to greater arrival differences of back-propagation pressure waves. The averaged peak pressure of back-propagation pressure waves in the air plenum chamber had the same change trend under multi-tube firing patterns. Single tube firing pattern resulted in the smallest pressure peak in the air plenum chamber and the pressure peak increased at the increased fired tubes.