This paper develops a theoretical model of long-term balanced population development，in which long-term balanced population development incorporates internal balance，external balance and overall balance of the population system leading to coordination and sustainability． According to the theoretical
model，the paper constructs an index system and evaluation model of long-term balanced population development，evaluating the extent to which balanced development，coordination and sustainability are achieved．An empirical analysis of the model is conducted using data from Sichuan Province over 1982-2010 to assess the long-term population development in Sichuan province． Results suggest that a great progress has been made in the long-term balanced population development of Sichuan in the past thirty years． However，challenges remain．