Abstract: At present, the basic idea of the study for monitoring crop harvest time is to predict the harvest time of crop by analyzing the relationship between the shape variety of NDVI curve and the significant change of crop morphology. However, this approach only considers the relationship between the change in the size of NDVI and harvest time, and only monitors the average harvest time in the whole region. Based on change vector analysis, choosing the summer maize in Yanzhou city as the study object and using the NDVI from HJ-CCD imagery covering maize harvest season in the research region in 2009 as the main data source, the study investigated the relationship between the change in the size and process of NDVI and the harvest time, and instantaneously monitored the harvest time of the summer maize fields. The precision verification for the result of remote sensing monitoring of harvest time was carried out through the survey samples, which the accuracy reached 89.65%. The spatial distribution of harvest time of maize was from the south to the north, which was basically consistent with the information offered by the Agricultural Bureau of Yanzhou city. The results show that change vector analysis as a new method through analyzing the change process of NDVI is effective for monitoring the harvest time of crop.