Concrete cracking is the significant stage of RC structural deterioration induced by steel corrosion. To predict the corrosion-induced cracking of the loaded RC structure, a multi-scale model is proposed. The formation and transport of corrosion products, which affect the volumetric expansion at the steel–concrete interface, are considered in this model. Then, based on poro-mechanics, the calculation of corrosion-induced stress in the pore structure of concrete is enabled. The corrosion-induced cracking of the practical component obtained from the proposed model shows a satisfactory agreement with the experimental observations. Then, the corrosion-induced cracking under different loading conditions are investigated. The results show that the effect of external loads on the time-to-cracking is moderate; the steel corrosion varies by no more 9% under different loading conditions at the surface cracking moment, whereas significant effects of the loading condition on the cracking pattern of reinforced concrete beams are found. Furthermore, the higher the load level, the more rapidly the corrosion-induced cracks develop; the maximum corrosion-induced crack widths on the surface of the beam subjected to 60% ultimate load is 1.14 and 1.22 times that of the 30% and 0% loaded beams, respectively, when reaching the serviceability limit state.