On the foundation of the analysis of current situation,future trend and target of major parameters of China's basic pension system for urban enterprise employees,including coverage fraction,actual contribution rate and replacement rate,this thesis predicted the income and expenses of pay-asyou-go pension funds in 2015-2050 under different assumed conditions,using population prediction data based on the sixth national census.The result shows that there would be deficit in different scale of payas-you-go pens...