Abstract: A method of data association in SLASEM(simultaneous localization and sampled environment mapping) is presented.According to the features that environment samples in the map have no one-to-one correspondence with the real environment and the traditional Mahalanobis distance cannot describe the similarity of two objects in SLASEM,a general distance function between two point sets is proposed for data association.The multi-association problem is solved by utilizing the topological structure of the environment.The result of data association in previous instant is also used to aid the data association in current instant.Results of two indoor experiments validate the effectiveness of the proposed algorithm.