Abstract:Abstract“Our Common Future”published in 1987 by the WCED of UN was the first report in the world to put forward the concept and connotation of sustainable development. Sustainability science fully reflects the human practice in various social activities, epitomizing a perfect integration in the relationship between“humanity and nature”and the inter-dependence between“man and man”. For the theoretical probe deeply into the essence, the paper extracts the three basic elements from sustainability science, i.e.,（1）sustainable motive power （DS）,（2）sustainable quality（QS）, and（3）sustainable equality（ES）. And, the author concluded a formula to pursuit the capacity maximum of sustainable development Max SD ={(DS,QS,ES)|φ1(DS)max,φ2(QS)max ,φ3(ES)max} in which, DS, QS, and ES were given on special meaning and rigid mathematical solution. φ1 ，φ2 ，φ3 and were the function forms of the prescribed substances.