TMCP treatment was carried out on B510L steel in different schedules in an experimental rolling mill. The effects of finish rolling temperature and coiling temperature on the mechanical properties and microstructures of the steel were analyzed. The tensile and impact properties were measured and the microstructures were observed by OM, TEM and SEM. With a proper control of rolling and cooling conditions, the yield strength of B510L reached 500MPa which was much higher than that of the steel in production now. The yield ratio and ductility of the experimental steel were also reasonable. It revealed that a good combination of ferrite with bainite microstructure was ideal for attaining good mechanical properties. It was also concluded that the strengthening mechanisms included solution hardening, fine ferrite grain hardening, bainite hardening and precipitation hardening. This work can provide an experimental basis for industrial productions.