Abstract: To study effect of obstacle shape on gas explosion flame propagation press, by using long straight experiment pipe, six obstacle shapes, which are circle, semicircle, cross circle, four circle holes, baffle and net, were selected to investigate the effect of obstacle shape on flame velocity and explosion overpressure in the pipe. The results show that, when gas concentration is 8%, flame propagates fastest for semicircle obstacle because of the effect of strong shock wave on unburned gas playing a key role on flame acceleration, while flame experiences relative slow propagation for other shape obstacles. When gas concentration is 10%, flame velocity is slowest for four circle holes and baffle obstacles. Effect of flame has little influence on shock wave and the distribution of explosion overpressure shows similar trend in different situations.