To improve the clearance surface roughness of non-assembly mechanisms fabricated by selective laser melting (SLM) and to manufacture non-assembly mechanisms with good surface quality and high density, the inclined surface roughness of the clearance is studied theoretically firstly. Then the clearance junction structure is designed. The effects of laser surface remelting and process parameters on surface roughness are analyzed, respectively. Results show that the inclined surface roughness (Ra) of the clearance is affected by inclined angle and the slice thickness theoretically. Ra decreases as the inclination angle increases and the slice thickness decreases. The clearance is designed as drum shaped hole to improve fabrication quality. Laser surface remelting process can not only improve the density, but also improve the surface quality. During the process, volume energy density should be controlled in success prototyping zone. When fabrication reaches the top of the clearance, the scanning speed should be increased to reduce the dross to improve surface quality. At last, the universal joint is fabricated successfully. The outside surface Ra is 8.25 μm, the clearance surface Ra is 12.47 μm, and the relative density is 99.1%.