Location is of great importance wireless sensor network applications because location information can often be used to identify events.TODA is a typical localization scheme widely used in previous work,but it requires time synchronization over all anchor nodes with known positions.Time synchronization increases the cost and complexity of system,and the errors caused by software and hardware seem subtle but often lead to bad accuracy of localization.A new TDOA localization scheme is presented in this paper,whose basic idea is to use an additional, position-known signal source,S′to change the way of calculating TODA values.After the emission of the source signal S,the new signal S′is emitted.The TDOA of S between different receivers can be derived from the time difference of receiving S and S′,called TD2S,at each receiver.This way eliminates the dependence of TODA on time synchronization,and improves the localization accuracy.Experiments under three-dimensional space have been conducted with mobile phones,and the results show that the proposed scheme is not only of high accuracy,but also of easy deployment,low cost,and robustness.