A unified method is proposed to treat 3D moving boundaries at arbitrary velocity as an extension of kinetic format and bounce-back format. Velocities at inlet and on solid wall are special cases of the model. A simplified expression is given in a three dimensional 15-velocity model. Numerical simulation for a diagonally lid-driven three-dimensional cavity flow is performed to verify this scheme. Compared with finite difference method (FDM), the proposed method proves reasonable.