In order to implement ignition at the same time at closed end of toroidal detonation tube,a way of ignition at a point and several branches of the same length was used.The results show that detonation wave can be formed immediately through shock produced by converging flame at the closed end of tube.With obstacles,the velocity of detonation will be decreased due to flow drag.Without obstacles,the velocity of detonation is close to the theory value.At about equivalence ratio 1.0,the flame velocity without obstacles may generate deflagration or detonation at random.And this random state can be avoided at equivalence ratio 1.1.