Uniaxial tension tests and hole-expansion tests were carried out to determine the influence of silicon on the microstructures, mechanical properties, and stretch-flangeability of conventional dual-phase steels. Compared to 0.03wt% silicon, the addition of 1.08wt% silicon induced the formation of finer ferrite grains(6.8 μm) and a higher carbon content of martensite(Cm ≈ 0.32wt%). As the silicon level increased, the initial strain-hardening rate(n value) and the uniform elongation increased, whereas the yield strength, yield ratio, and stretch-flangeability decreased. The microstructures were observed after hole-expansion tests. The results showed that low carbon content martensite(Cm ≈ 0.19wt%) can easily deform in coordination with ferrite. The relationship between the mechanical properties and stretch-flangeability indicated that the steel with large post-uniform elongation has good stretch-flangeability due to a closer plastic incompatibility of the ferrite and martensite phases, which can effectively delay the production and decohesion of microvoids. Uniaxial tension tests and hole-expansion tests were carried out to determine the influence of silicon on the microstructures, mechanical properties, and stretch-flangeability of conventional dual-phase steels. Compared to 0.03 wt% silicon, the addition of 1.08 wt% silicon induced the formation of finer ferrite grains (6.8 μm) and a higher carbon content of martensite (Cm ≈ 0.32 wt%). As the silicon level increased, the initial strain-hardening rate (n value) and the uniform elongation increased, The results of that low carbon content martensite (Cm ≈ 0.19 wt%) can easily deform in coordination with ferrite. The relationship between the mechanical properties and stretch-flangeability indicated that the steel with large post-uniform elongation has good stretch-flangeability due to a closer plastic incompatibility of the ferrite and martensite phase s, which can effectively delay the production and decohesion of microvoids.