Based on the daily precipitation data and agricultural flood disaster data in Hainan Island from 1966 to 2015, the grey relation analysis method and correlation analysis method were used to revise the monitoring indicator of agricultural flood disaster. The agricultural flood disaster monitoring indicator was gradually selected by combining with historical flood records and agricultural areas suffering from agricultural flood disaster, the temporal and spatial distribution features of agricultural flood disaster were analyzed in the area for nearly 50 years using this indicator. The results are as follows:(1) The agricultural flood monitoring indicator was the initial indicator threshold plus 22 mm in Hainan Island. The agricultural flood index which was calculated by revised indicator had significant correlation with the agricultural flood-affected ratio, the inundated rate and the barren rate, and the correlation coefficients were 0.36 (P<0.05), 0.53 (P<0.01) and 0.40 (P<0.05), respectively. (2) The frequency of large agricultural flood increased relatively in the rest of the time in Hainan Island except the 1980s in which it decreased obviously. Meanwhile, the agricultural flood areas concentrated on the central and eastern regions and gradually expanded from the central and eastern regions to the northern and western regions.