The invention discloses a profile modification method for involute spur cylindrical gear pairs and a matched dedicated parameterized CAD system. The method mainly comprises the steps of establishing a universal composite profile modification curve equation, and then obtaining multiple first composite profile modification curves and second composite profile modification curves for use by means of an orthogonal experimental method; after simulation modification, conducting simulation transmission testing on the gear pairs one by one so as to screen out first composite profile modification curves and second composite profile modification curves meeting design requirements; by means of the matched dedicated parameterized CAD system, fusing modeling of the involute spur cylindrical gear pairs after profile modification, meshing simulation analysis and extraction of meshing performance indexes of the profile modification gear pairs into one system. The profile modification method is high in universality and stable and reliable in modification quality. The CAD system has multiple functions, is convenient to operate, and can be efficiently used for auxiliary design during gear research and development.