Abstract: The high speed mash seam welding experiments were conducted on two kinds of deep-drawable cold rolled steel sheets with thickness ranges of 0.5 to 1.5mm.The influence of welding parameters and annealing treatment on microstructural distribution and tensile strength of the joints was investigated. The elevated temperature tensile behavior was also investigated using a Gleeble 1500 machine. The results shown there were fiber zone, partially recrystallized zone, fine grain zone, coarse grain zone and unequilibrium microstructure zone in the as-welded joint. There were fine grain zone, coarse grain zone and unequilibrium microstructure zone in the annealed joint. The tensile strength of the as-welded joint was greatly reduced when there was crack, resulted from splash or incomplete fusion, in the weld. A joint with higher strength at as-welded state had higher strength at annealed state or at elevated temperature. Joint strength was higher than that of base metal in recrystallized state, and lower than that of base metal in non-recrystallized state.