Ultra-wide Band (UWB) ranging indoor positioning is widely used in shopping malls, residents, hospitals and other places, improving the competitiveness of indoor positioning is positioning accuracy. In order to achieve accurate ranging under various interference conditions in the actual measurement process, Kalman filter algorithm is adopted to reduce the influence of external interference on ranging as much as possible, so as to reduce the measurement error. Aiming at the problem of UWB ranging accuracy improvement, a comparative experiment using Kalman filter as processing algorithm is designed. The results show that the ranging accuracy has been greatly improved, and the error has been reduced from 5.8% to 2.44% in the experimental environment. In the distance where the accuracy is most obviously improved, the data reliability has been improved and the ranging accuracy has been improved by 58% through drawing analysis. Experimental results show that Kalman filter can effectively improve the ranging accuracy of UWB.