The microstructure of Ti-6Al-4V joints by laser beam welding with different welding parameters was studied, and the tensile properties were investigated. The microstructure of welding seam by laser beam welding consists mainly of α′ martensite phase as well as some α″ phase. By increasing the weld heat input，the distribution of martensite becomes more dispersive and glomerate due to the molten pool stiring, the welding stress and the burning loss of alloy elements. However, the welding parameters have no obviously effects on both the phase composition and the phase ratio. The tensile strength of joints is higher than basal metal when welded with reasonable parameters