Surface flattening is a crucial problem for many applications such as aircraft design, vehicle design, garment design, etc. This paper presents a robust and efficient surface flattening approach based on energy model. First, a triangular mesh model is used to present a complex surface. Then, an optimizing model based on energy function is used to flatten the 3D triangular mesh into 2D planar patterns. The method is an iterative procedure, which incrementally flattens the 3D triangular mesh by region growing and obtains 2D planar patterns by reducing the stretch. Our method optimizes angle and area stretch simultaneously, so the flattening does work with less global distortion and without flipping. Experiments show that the proposed method can obtain better results.