The problem of automatic construction of a composite bicubic Bezier surface approximating a given parametric surface to a required tolerance is discussed in this paper. Algorithms for Bezier patch boundaries construction and iterative optimization of internal patch control points are developed to construct an approximating surface. The approximating surface is constructed to be approximately continuous at patch boundaries which allows to achieve higher global smoothness. The required approximation tolerance and patch junction smoothness is achieved by means of iterative subdivision. The technique is designed for conversion of parametric surfaces of special type to a universal surface representation format - bicubic Bezier spline surface. This is necessary both for uniformity of surface representation within a single CAD system and for data exchange between different CAD systems. Industrial implementation of the technique was made within a system for computer-aided design of aerodynamic models of the Central Aero-Hydrodynamic Institute GeMMa-3D.