The invention provides a pedestrian re-identification method and system based on an irregular video sequence. The method comprises the following steps: detecting stable points in a state curve and extracting a plurality of continuous subsequences from the video sequence to obtain a candidate sequence; calculating reconstruction errors of each subsequence through sparse representation, and obtaining a noise measurement result of each subsequence; according to the noise measurement result of each subsequence, removing the subsequences, the noise of which is larger than corresponding thresholds, from the candidate sequence, and constructing a candidate pool; and carrying out adaptive weight pedestrian feature representation to obtain a retrieval result based on the video sequence. The method and system improve pedestrian re-identification performance under the irregular sequence, can be widely applied to the monitoring field, video analysis and other multimedia applications, are high in precision and good in effect and have an important market value.