Abstract: This paper presents a DC/DC converter inductor current observer based on improved extended Kalman filter, which can reduce output voltage noise caused by electromagnetic interference and eliminate the steady state error when load changes. Firstly, the State-space equations of boost DC/DC converter and extended Kalman filter are introduced. Secondly, the load estimation algorithm is proposed to improve the extended Kalman filter. The improved extended Kalman filter can use output voltage, inductor current and duty radio to estimate actual load value. Therefore, the parameters of improved EKF can be updated in real time and current observer can estimate inductor current accurately. Finally, the validity of the proposed approach has been demonstrated by simulation. The simulation results show that the improved extended Kalman filter can filtering the output voltage noise caused by electromagnetic interference effectively, and estimate inductor current precisely, which ensures the accuracy of the output voltage.