Welding experiments of DP780 high strength steel plate produced by Baosteel with IPG YLR-6000-ST2 fiber laser have been processed. The influence of welding parameters on welding quality has been investigated. As well as microstructure and mechanical character of welding seam have been analyzed. The results show that the joint appearance of DP780 high strength steel welded with IPG YLR-6000-ST2 fiber laser has good performance and the mechanics property is good without fit-up gap. The microstructure of weld bead is columnar crystals, mainly lath-shaped ferrite, needle-like lower bainite and a small amount of martensite. Heat-affected zone is narrow and the grain grows with little size. The measured micro-hardness values of the sample decrease smoothly from weld center to base metal and there does not have softened zone.