Abstract: An estimation algorithm for driving resistance load of Electric Vehicles (EV) has been proposed in this study. Driving resistance load is an important factor in the motion control of EV. It is a large and time varying disturbance, so it is difficult to measure and unable to be compensated only by the design of robust controller. Therefore, an approach using an unknown input observer is introduced to estimate driving resistance load. The effectiveness of the observer-based methods is proved through the XJTUEV (Xi`an Jiaotong University EV)-1 simulation model in different road conditions.