Inhomogeneity of optical glass used in high-precision optical system influences the imaging quality of the system. This kind of inhomogeneity can be expressed by Zernike polynomial expression with the discrete refractive-index data measured by ZYGO interferometer, in order to use the Fourth Order Runge-Kutta method for ray tracing. Due to the randomness of the material′s refractive-index distribution, using different part of one piece of semi-finished optical glass to manufacture lenses with same parameter and rotating manufactured lens different degrees around the optical axis would influence the optical system′s performance.