We analyze the method based on TOA(Time of Arrival)which is appropriate for UWB(Ultra Wild- Band)system,among classical localization technologies,and presents the theoretic analysis and simulation re- sults of the relative localization estimation with UWB in WSN(Wireless Sensor Networks).We prove the superi- ority of TOA localization method adopted in UWB system.In a single-hop WSN,the more the blindfolded nodes number the better localization precision is,in a multi-hop WSN,when the number of reference nodes is certain, the more links between blindfolded nodes and reference nodes,the better localization precision is;the more hop count,the worse localization precision is.