Abstract: A novel localization scheme for wireless sensor networks (WSNs) is proposed based on the joint estimation algorithm of TOA (time of arrival) and AOA (angle of arrival) under UWB (ultra wideband) signaling. One reference node is enough for the proposed method to localize other sensor nodes in 2-dimension, and the synchronization of the network is not necessary, satisfying the low complexity requirement of WSNs. RTT (round trip time) is used to estimate TOA, and the multi-path detection algorithm for TOA estimation is presented. TDOA is adopted to estimate AOA, avoiding the complicated antenna beam-forming for AOA. Simultaneously, the error model to the localization performance of the proposed scheme is theoretically analyzed and tested under IEEE 802.15.4a channels. The results demonstrate the effectiveness of the proposed scheme.