Silver-based high reflectance coatings are widely used in space optical system.While silver is soft and has poor adhension to dielectric material used as substrate.Bonding layers are often added to overcome its major deficiency when silverbased reflectors are fabricated.The first principle method is used to study the improvement of adhesion owing to introducing Cu as bonding layer.When silver-based mirrors used in high temperature,diffusion of silver and copper will occur,the influence of diffusion to optical performance is also discussed and the experiment results are also given.