Developing green economy and improving green development efficiency are the inevitable choices for China to take the road of high-quality development. Based on the super-SBM model containing unexpected outputs, the green development efficiency of 26 cities in the Yangtze River Delta urban agglomeration is measured. The Theil index and kernel density estimation are used to examine its spatial differences and dynamic distribution trends. Based on human capital theory, it incorporates technological talent agglomeration into a regression model to explore the driving factors of green development efficiency. The results show that, the green development efficiency of 26 cities in the Yangtze River Delta urban agglomeration is fluctuating and rising from 2007 to 2019. But the differences among cities are significant, and the differences within the province is the main source of overall regional differences. Furthermore, the kernel density estimation shows that the overall dispersion degree of green development efficiency of each city is expanding, which means the concentration degree of efficiency value decreases and the characteristics of polarization gradually appear. There is an inverted U-shaped relationship between the concentration of scientific and technological talents and the green development efficiency of the Yangtze River Delta urban agglomeration. And the level of economic development and industrial structure have a significant positive impact on the green development efficiency.