Aiming at the request of education academies and mid & small-scale corporations, conventional UV optical source systems in stereolithography apparatus were replaced with Ultraviolet Light Emitting Diode (UV LED) in the paper, and a LED optical system based on a single UV LED was designed. In the system, the beam from the single LED was focused through a multi-lens optical focusing system, and the LED chip was controlled with close-loop control strategies in order to keep steady operation. Experimental results show that the optical system meets the design request and has the advantages of simple structure, long stabilization and maneuverability. Compared with the other light sources in the stereolithography apparatus, the outstanding characteristics of the system are lower cost and higher performance on the condition of meeting speed and accuracy.