Abstract: A new MEME-based motif discovery algorithm for uncertain data stream is proposed by using the idea of sequential pattern discovery in bioinformatics. According to features of uncertain data stream, the new algorithm designs a simplified calculation method for uncertain sliding window and modifies the SAX symbolic strategy. The feasibility of the proposed algorithm is verified by one uncertain test data stream from air and missile defense sensors. And its accuracy is measured through planting different number motifs. Furthermore, the proposed algorithm is validated by comparing with existing algorithms in the condition that the existence probability of tuples is set to 1.