Mechanism that is designed and assembled digitally and lately manufactured directly without post-assembly is called non-assembly mechanism. Selective laser melting (SLM) is a desirable technology for manufacturing non-assembly mechanisms directly since it is able to manufacture functional parts with metallurgical bonded, relatively high density, high dimensional accuracy and favorable mechanical properties. The critical factors of manufacturing non-assembly mechanisms by SLM such as display strategy, dimensional accuracy and surface roughness of clearance character, structural optimizing of clearance character, etc are investigated. Non-assembly mechanisms such as copper cash abacus and collapsible abacus, planar linkages (slider-crank, crank-rocker, and rocker-slider) and universal joint, etc are freely designed and are manufactured by using DiMetal-100 series SLM equipment. It is shown that SLM can not only manufacture parts with complex structures successfully, but also can manufacture non-assembly mechanisms with relative motion directly. It provides a feasible method for the digital design and integrated manufacture of mechanical and electronic products.