The effect of Si content on the microstructures and growth kinetics of intermetallic compounds (IMCs) formed during the initial interfacial reaction (<10 s) between solid steel and liquid aluminum was investigated by a thermophysical simulation method. The influence of Si addition on interfacial mechanical properties was revealed by a high-frequency induction brazing. The results showed that IMCs layers mainly consisted of η-Fe₂Al₅ and θ-Fe₄Al₁₃. The addition of Si reduced the thickness of the IMCs layer. The growth of the η phase was governed by the diffusion process when adding 2 wt.% Si to the aluminum melt. When 5 wt.% or 8 wt.% Si was added to aluminum, the growth was governed by both the diffusion process and interfacial reaction, and ternary phase τ₁/τ₉-(Al,Si)₅Fe₃ was formed in the η phase. The apparent activation energies of the η phase decreased gradually with increasing Si content. The joint with pure aluminum metal had the highest tensile strength and impact energy.