In recent years there have been extensive studies on III-V semiconductor quantum dots (QDs). In this paper we have formulated the absorption spectra of a realistic QD system with dot size distribution described by a Gaussian function. The dots were approximated as cubic boxes having finite potentials at the boundaries. The effects of size non uniformity on the optical absorption spectra of a realistic QD system was analyzed and the results have been compared with ideal dots having infinite potentials at the boundaries.