Abstract: Taking Sanya city as the research subject during2005-2013, from the three sub-systems of the natural ecological system, social ecological system and the ecological economic system, and by employing the principal component analysis, an overall grading is conducted to evaluate Sanya ecological system. The evaluation shows that the ecological system of Sanya undergoes a slight fall in the years of2005-2006, and in2006-2013 the various indices are steadily improving, the rather large load value of the first principal component indicators reveals that human activities have an increasingly severe influence on the e- cosystem; the rather large load value of the second principal component indicators reflects the degree of environmental pollution and resource utilization in Sanya city, the ups and downs in numerical values show that the effect of industry on ecosystem is
fluctuating. It is concluded that the urban ecosystem in Sanya is undergoing benign development on the whole.