To select appropriate support structures in foundation pit engineering of underground tunnels for the Hong Kong International Airport (HKIA), this paper proposed the use of inclined-vertical combined interlocked steel pipe piles, which are beneficial for support, water isolation, and recovery. Numerical simulations were conducted using finite element software Midas GTS NX to analyze the effect of different combination types and inclination angles on the engineering response of the inner-row piles of inclined-vertical combined double-row interlocked steel pipe piles. The results show that the inclined-vertical combined double-row piles reduce the horizontal displacement at the top of the inner-row piles by approximately 50% and decrease the peak bending moment by around 30%, yielding better engineering performance than traditional vertical double-row piles. When the inclination angle of the inner-row piles is the same, the positive-negative inclined double-row piles outperform other combinations in controlling the horizontal displacement at the top and reducing the peak bending moment and the deflection of the piles. In engineering practice, it is recommended to prioritize positive-negative inclined double-row piles or inward-vertical inclined double-row piles, and to maximize the inclination angle within the allowable limits of construction equipment. This can lower the horizontal displacement at the top, peak bending moment, and deflection of the piles to ensure the stability of foundation pits.