In this paper, a laser welding experimental platform for narrow and burred seam welding (with seam width less than 0.1 mm) of complex three-dimensional (3D) surface based on eight-axis machine tool is introduced. A novel vision sensor system (which is named as HUST-SM) which based on visual information fusion of 3D and two-dimensional for detecting the narrow and burrs welding seam is also presented. Several experimental tests are applied to verify the features of this platform and the HUST-SM vision sensor system. Experimental results show that the vision sensor system has high precision and resolution for obtaining narrow seam information. The narrow seam of space curve welding tests demonstrates that the narrow seam welding can achieve high finish quality.