Abstract: In order to protect location estimates from NLOS (non-line-of-sight) error influence, a high-accuracy cooperative positioning algorithm was proposed. In this algorithm the cooperative information between MSs (mobile stations) is used to enhance the location accuracy, and the relationship between measured TOA (time of arrival) and SF (sentinel function) defined by GIS (geographic information system) is utilized to identify NLOS. The detailed performance analysis of the algorithm was given. The simulation results show that under a multipath environment, the proposed algorithm has a significantly high location accuracy compared with the existing algorithm. The probability of location error less than 90 m is enhanced from 53% to 98% under the condition that five MSs in eight cooperative MSs are under an LOS (line of sight) environment.