A two-body model is an essential configuration of the aerospace vehicle, e.g., two-stage-to-orbit vehicle. Unsteady numerical simulations are performed to investigate the hypersonic flow over a parallel-staged double-wedge configuration of the different angles of incidence (AoI) at Mach 7. The effect of the AoI on the unsteady flow is analyzed, and the flow mechanism of the periodic flow oscillation associated with shock interactions is clarified. The unsteady oscillation flowfield is caused by propagation and inversion of the pressure gradient between the upstream and downstream in the interstage clearance. Moreover, the Strouhal number ( St ) of the oscillation flowfield is determined and analyzed, namely, the dominant nondimensional frequency is 0.20 <  St < 0.26, and the oscillation frequency is determined by the propagation's speed and distance of the pressure gradient. Particularly, the flow tends to steady at AoI ≤ 3 deg; else self-sustaining periodic oscillation flow at AoI > 3 deg tends to be stronger with increasing AoI. The mechanism that accounts for the division condition of the AoI whether the steady or unsteady flowfield of the double-wedge configuration is also clarified, namely, the relationship between the local shear layer height and the orbiter's nose height which is governed by the incidence angle determines whether the oscillation flowfield pattern occurs or not.