On the basis of drought disaster occurred frequently in Southwest China in recent years, water suitability of regional vegetation was discussed. An important scientific issue concerned with the seasonal drought disaster was analyzed. The issue was whether could ecological water demand of Eucalyptus plantation and Hevea plantation be adapted to regional precipitation condition, or whether could ecological water demand of Eucalyptus plantation and Hevea plantation break the balance of supply and demand of regional ecological water use, and even lead to regional drought disaster. Research status and development trends in water suitability of regional vegetation were analyzed. It was pointed out that no great progress and no symbolic achievement was gotten in research related to water suitability of vegetation that based on the calculation of ecological water demand of vegetation. As for research on ecological water demand of vegetation, the basis for assessment of water suitability of vegetation, there are some problems left. Water suitability of typical vegetation in Yunnan Province and relationship between ecological water demand of regional vegetation and regional drought disaster should be investigated.