The metallographic phases and tensile strength of tailored fiber laser welded blanks of Al-Si coated Usibor1500 and Usibor1500 without coating are investigated, and the distribution of Al in the weld seams is investigated by energy- dispersive X- ray spectroscopy (EDS). Ambient tensile strength is tested to study the difference with or without top coating layer. The results show that, Al enters the weld seam and distributes in the whole area of weld seam and be with local segregation, the mass percent of Al in two phases are 1.76% and 2.65% , respectively. Al- Si coating which entering the weld seam decreases the mechanical properties of weld seam due to the formation of brittle phase, whose strength is 458~479 MPa, while the strength of base metal is around 500 MPa. After removing the top layer of the coating, the mechanical properties increase distinctly, whose fracture locations are consistently at the base metal.