Abstract: In order to study the influence of back pressure on the formation of thick-walled optical lens, an experimental scheme for the layered-back-pressure injection-molded thick-walled optical lens was developed in this work, and an optimization experiment for the process parameters was conducted by the orthogonal experiment optimization design. The effect of the inner and outer back pressures on the optical properties of the thick-walled optical lens in an layer mode was investigated so as to fabricate an ideal thick-walled optical lens with excellent optical properties on the basis of the orthogonal optimization parameters. The orthogonal experimental results indicated that the shrinkage of the thick-walled optical lenses could be reduced effectively by use of PMMA as a raw material during the layered back-pressure injection molding process. The light transmittance and refractive index of the thick-walled optical lens were improved with an increase of the back pressure of the inner and outer layers, indicating excellent optical properties.