In this paper, a technique of fabricating spherical surface microlenses by laser chemical vapor deposition (LCVD) was introduced. The theoretical analysis and the experimental system of spherical microlenses deposited by LCVD are giren. Under certain conditions of deposition the thickness profile and the optical focusing characteristic of microlenses were simulated with computer. Plano convex silicon nitride microlenses with spherical surface on flat quartz substrate was successfully fabricated and their parameters were measured. The experimental results indicated that through controlling the chemical mixture ratio and concentration of source gases properly adjusting the laser power and spot size on substrate, and selecting appropriatelly the deposition time the transparent plano-convex silicon-nitrid microlenses with smooth spherical surface and different diameters could be obtained.