Abstract: This paper firstly delineated the sphere of influence of Shanghai, Nanjing and Hangzhou by gravity model. Then economic areas of Shanghai, Nanjing and Hangzhou were defined by their center and sphere of influence. Thirdly, regression analysis was used to capture the relationship between population density and distance to the Shanghai, Nanjing and Hangzhou. Results show that logarithmic model fitting the regional density patterns the best in China has better goodness of fit than linear model, exponential model, and power model. For further exploration, four Quadratic models based on above four basic models (linear model, logarithmic model, and log transformed exponential model and power model) are tested. Logarithmbased Quadratic model is proved to be the best model to describe the population density patterns in economic areas of Shanghai, Nanjing and Hangzhou for its highest coefficient of determination (Rsquare) in all eight models mentioned above. Based on the change of fitted logarithmbased quadratic function profiles over time, regional growth patterns can be identified. Strong trend of centralization and near field spread are the main characteristics of growth pattern in Shanghai, Nanjing, and Hangzhou economic area during 1982 and 2010. However, differences of growth pattern can be seen in different regions and different periods.