Abstract: This paper studies different methods of spacecraft de-orbiting in order to find a proper way for de-orbiting spacecrafts in the low earth orbit (LEO). Advantages and shortcomings of these de-orbiting methods were analyzed to show that the Electro-dynamic Tether de-orbiting system was the most economical and efficient. A mathematic model is proposed for Electro-dynamic Tether, and is used to estimate de-orbiting time. The simulation with MATLAB shows that a fast decay is effected by the electro-dynamic drag for LEO spacecrafts.