Laser welding,as a new type of welding method for titanium alloy parts on aircraft,has been widely concerned at home and abroad. TC4 laser butt welded joints with different power from penetration to incomplete penetration were prepared. The microstructure and microhardness distribution of different parts under different process parameters were observed and analyzed,and the corrosion resistance of different parts of welded joints in marine environment was studied by electrochemical method. The results show that the microstructure in the molten pool changes from equiaxed dendrite to lamellar α/α′ phase in β grains due to the penetration of specimen caused by increase of laser power.the size of equiaxed dendrite increases,α/α′；The lamellar thickness decreases；The hardness fluctuation of the welded joint along the test line increases as the increase of power,and the hardness distribution is the most uniform when the laser power is 550 W.