In this paper, numerical simulation study was carried out to study the combustion rule and the flow field characteristics of propane-air premixed gas in different angle bending pipes with Realizable model and turbulent flame closure combustion model. The results show that the bending structure of the pipe has a significant effect on the flame front and the surrounding flow field. With the increase of the bending angle, the resistance effect of the bending pipes on the airflow becomes stronger, and the separation of the flame and the concave wall is more obvious. However, the flame propagation velocity increases first and then decreases with the increase of the bending angle. When the bending angle is 120 degrees, the incentive effect of the concave wall side reflected wave on the combustion reaction is the strongest and the attenuation effect of the convex wall side sparse wave on the combustion reaction is the weakest. Meanwhile, flame propagates the fastest, which is increased by 80% compared with that in straight pipe. When the shock wave passes through the bending pipes, the analysis on characteristics of pressure field shows that under bending pipes with different angles, the distance recovered from the curved shock wave to the plane shock wave is 3-5 times of the equivalent diameter.