Bridge structure was prepared with TC4 titanium by selective laser melting. The effects of process parameters and span lengths on surface roughness of under bridge surface, density and forming angle of under bridge surface before and after sandblasting were studied. The results show that with the increase of span lengths, the density and the forming angle of under bridge surface decrease. When the span lengths is 6 mm, the edge of the forming angle of under bridge surface disconnects with the vertical overhang surface. By optimized the process parameters, when the span lengths is 4 mm, the laser power is 285 W and the point spacing is 50 μm, the comprehensive performance is best on surface roughness of under bridge, density and forming angle of under bridge surface. After sandblasting treatment, the density is increased by 4%-15% and remains stable, and the maximum density is 98.73%. The forming angle of under bridge surface become smaller, and the minimum forming angle is 21.7°. The changing trends of forming angle of under bridge surface by different process parameters are similar with before sandblasting. Through the observation of the microstructure of TC4 sample, the microstructure of TC4 sample is occupied by acicular martensite α′ phase.