The main optical system of Space Solar Telescope is composed of primary mirror, collimating lenses and imaging lenses. To satisfy imaging demands of wide range of wavelength (393nm- 656nm), the collimating lenses are composed of five components of which decentering errors are extremely stringent. To satisfy above situation, elastomeric mounting of lens is introduced for each component. The basic centering principle is discussed, the subcell assembly is introduced for the elastomeric mounting. Two aligning methods of are introduced for the alignment of subcells. Athermalization formulation of subcells is given. Besides, finite element model of such mounting is established for analyzing temperature change and elastomer shrinkage effects to lens surfaces.