Bézier curve and surfaces are one kind of the most commonly used parametric curves in CAGD and computer graphics. Developingmore convenient techniques for designing and modifying Bézier curve and surfaces are an important problem. This paper investigates the optimal shapemodification ofBézier surfaces by geometric constraints. A constrained optimizationmethod based on changing the control points of the surfaces is presented in this paper. Ahich modifys control points of the originalBézier surfaces to satisfy the given constraints andmodify the shape of the surfaces optimally. Practical examples are also given. The results indicate thatLagrange multipliermethod is an effective way to solve the problem of shape ofBézier surfaces.