For IOT wireless sensor networks, there is large positioning error in APIT positioning algorithm, an improved APIT positioning algorithm is proposed. APIT test is easy to produce InTo Out and OutToIn errors to affect positioning accuracy, a new interior point test method is designed; the new algorithm further reduce the triangular area in the traditional APIT positioning algorithm through the median line, the positioning accuracy is improved. The algorithm does not require any additional hardware support to improve complexity. The simulation results show that the improved algorithm has high localization accuracy in the network anchor node density and different communication radius, it can meet the needs of most localization wireless sensor networks.