This paper discusses efficiency, spatial pattern characteristics and impact mechanism of green development in ChengduChongqing City Group from 2005 to 2018 by using various methods such as the SBM model, spatial autocorrelation analysis, and the spatial panel metrology model. It is found that the green development efficiency of Chengdu-Chongqing City Group has been gradually improved as a whole with decreasing regional differences year by year; the green development efficiency of the city group has a significant positive spatial autocorrelation and spatial combined effect. There are other factors with obvious indirect effects, including economic growth, urbanization ratio, industrial structure, pollution index, population scale, foreign direct investment and marketization level, and so on. However, the direct and indirect effects of government intervention and human capital offset each other in opposite directions; thus, the total effect is no longer of significance. In addition, some factors are of insignificant indirect effects, such as government intervention, patent quantity, and population, indicating that these factors have no obvious influence on the green development efficiency of neighboring areas.