Abstract: Trajectory pattern mining is an important topic of knowledge discovery.Due to the limitations of location device,the trajectory data are not certain.The paper focuses on mining uncertain trajectory patterns.With the introduction of fuzzy set,a novel method is proposed to deal with uncertain trajectory data pattern mining.Firstly,the work space is divided by a grid whose cells are size uniform.The degree of membership of uncertain points relative to cells is calculated based on the probability distribution of moving object's real position.Then obtain the regions through the uncertain regions of interest extracting method.Uncertain trajectory pattern mining is done based on regions of interest.Finally,the experiments show the effects of uncertain trajectory pattern mining using fuzzy theory.