A low carbon SiMnTiNb ultra-high strength hot-rolled strip steel with yield strength of 700MPa was developed by thermo-mechanically controlled processing (TMCP) on a conventional 1450mm hot strip production line. Continuous cooling transformation (CCT) diagram of the industrially produced steel was constructed. Precipitation-hardening behavior was analyzed by the hardening response of a series of aging experiment. Mechanical properties, cold bending property, and weldablity of the industrially rolled strip were tested. The microstructure of the strip consists of fine ferrite grains sized at 4-5μm containing precipitates of Nb-Ti, bainite and martensite. The ultra-high strength is attributed to grain refinement, precipitation and phase transformation hardenings，etc. Cold bendability and welding properties are satisfactory.