This study analyzed the spatial and temporal variations of PM_2.5 concentration and the degrees of urbanization for the five periods of 2001~2003, 2004~2006, 2007~2009, 2010~2012, and 2013~2015 in Mainland China, on perspectives of population, land and economy. Scissors difference method, correlation analysis and geographically weighted regression (GWR) model were employed to explore their relationships. Results showed that the three-year average degrees of urbanization for population, land and economy increased steadilyand PM_2.5 concentration fluctuated in an increase direction (44.14~50.89μg/m³). However, rates of these variations were different between four economic regions. Spatial distributions of PM_2.5 concentrations were similar for the five periods, they were high in Beijing-Tianjin-Hebei (BTH) area, north Henan and Shandong province, and west Xinjiang. The area with high urbanization degree increased gradually. Angles (15.33°~62.92°) between the two tangent lines of temporal variation curves of degree of urbanization and PM_2.5 concentrations based on scissors difference method revealed the insignificant relationships between them temporally. In addition, significant association was found between the spatial distributions of PM_2.5 concentrations and the degrees of urbanization. The degrees of urbanization for land were positively correlated with PM_2.5 concentrations at the 0.01level. The sequence of correlation coefficients from high to low was Northeast (0.609~0.723) > Midlands (0.572~0.631) > East (0.218~0.323) > West (0.079~0.255). Except for Midlands and West, the degrees of urbanization for economy had significantly positive effect on PM_2.5 concentrations, while those for population were negatively associated with PM_2.5 concentrations in Eastern area. The results for GWR models further demonstrated this varied spatial association with adjusted R² were found to be the highest in 2001~2003 period (0.6~0.77) and the lowest in 2013~2015 period (0.08~0.64).