δ- transformation induced plasticity（TRIP） steel has performed high strength combined with excellent ductility，which satisfy the requirements for the third generation advance steels for automotive application. In addition，it could to be spot welded. It’s high potential to be industrialized for both manufacture and automotive application. The development of δ-TRIP，microstructure and mechanical properties，transformation and microstructure evolution，strength and toughness mechanism will be reviewed. The process and physical metallurgy for resistance spot welding will be discussed as well.