Composites are widely used for the aircraft, train and automobile. There are so many threat of damage from various reasons such as accident, impact by the bird, thunder lightening, and handling damage. Composites are generally used for a part of complex module, so it is not easy to replace damaged parts. Most of composites are structural material, so it has to endure designed load. There are three repair techniques: patch repair, scarf sanding repair, stepped sanding repair. This research is consisted of the effect of scarf angle and step distance on composites repair process. For these objectives, computer aided FEM(Finite element method) analysis is achieved. Result of these analyses can be an extra guide to establish composites repair standard.