a b s t r a c tOblique detonation waves are simulated to study the induction zone structures with different incident Ma numbers. Three kinds of shock configurations are observed at the end of the induction zone, which are the k-shaped shock, the X-shaped shock and the Y-shaped shock. The X-shaped and Y-shaped shocks appear when the incident Ma is low, and the Y-shaped shock associated with the complicated unstationary process. The induction zone length reaches the maximum value when the X-shaped shock changes into the Y-shaped shock, which indicates different mechanisms deciding the induction zone. The oblique shock wave dominates the induction zone when the incident Ma is high, while the oblique detonation wave dominates the induction zone when the incident Ma is low.