Based on unstructured grids, codes for 3D aerodynamic shape optimization are developed using Euler equations′solution, continuous adjoint method, free-form deformation (FFD) strategy， and sequential quadratic programming (SQP) optimization method. Fortran 90 is used for the dynamic storage of arrays and pointers and for saving memory. Second-order Roe-type upwind scheme and LU-SGS scheme are used to solve the continuous adjoint equations, and a new approach to computing parametric coordinates is adopted so that FFD can be robuster. The gradients of the adjoint method are compared with those of the finite difference. The designed system is successfully applied to ONERA M6 wing transonic shape optimization with the purpose of reducing drag, and the result shows that the system is reliable and efficient for reducing drag design.