TMCP treatments were carried out on B510L steel followed by using a pilot rolling mill. Effects of finish rolling temperature and coiling temperature on 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 500MPa was obtained, which was much higher than that in normal production. The yield ratio and ductility of the experimental steel were also reasonable. It was revealed that a good combination of ferrite with bainite microstructure was ideal for 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.