The numerical investigation on the detonation tube for simulating the exhaust gas of rocket combustor are examined with the various cross-sectional area ratio A/A*, initial gas pressure and equivalence ratio. Preliminary experiment on detonation tube is also conducted to obtain its primary operation characteristics for the engine test. Numerical study suggests the operation time t, which is normalized by the length of the detonation tube, as the duration time of plateau pressure and presented for each initial pressure and equivalence ratio of the detonation tube. The effect of A/A* is examined by changing the geometric term of governing equation, and the plateau pressure is observed in all A/A* cases. As the A/A* increases, the plateau pressure increases due to the regulation effect of the throat. The throat gas composition and pressure are presented for each initial gas condition, and the linear relation of the throat pressure and the initial pressure are exhibited. In the experiment, the pressure history shows the pressure rise due to the exhaust gas through the detonation tube. A typical DDT phenomenon is observed in the detonation tube, and it causes the reduction of the operation time τ predicted by numerical results.