The modern Low (Ultra-low) Carbon Bainitic Steel (ULCB) is a high-strength, high-toughness and multi-application steel. Its appearance is the consequent result of the social need and the development of the modern metallurgy technology in recent 30 years. Due to the sharp reduction of the carbon content in the steel, the disadvantageous effects of the carbon on the toughness of the bainite microstructure is eliminated completely, and the fine bainitic matrix microstructures with a high dislocation density can be obtained with the controlled rolling and controlled cooling. The strength of the steel does not depend on the carbon content in the steel any more, and it is primarily guaranteed by the following methods: fine grain strengthening (microstructures), dislocation and substructure strengthening, the precipitation strengthening due to the micro-alloying elements such as Nb, Ti, and V, as well as the sediment strengthening of the ɛ -Cu. The strength and the toughness of ULCB steel match perfectly, and especially the steel has excellent field welding performances and the capability of resisting HIC (hydrogen induced cracking). In the end of chapter, a theoretical concept is proposed for the further fining on the basis of the overview of fundamental microstructures and performance characteristics of the new steel. A theoretical concept is proposed for the further fining.