The impact of green investment on high-quality economic development and carbon emission reduction will not only change with the growth of investment scale, but also vary with different investment fields and methods, resulting in non-linear relationships and heterogeneity in investment types. Based on the provincial panel data of China from 2003 to 2019, this paper empirically tests the non-linear relationship between green investment and high-quality economic development and carbon emission intensity by using the spatial Durbin model (SDM) and semi-parametric panel spatial lag model. The results show that there is a significant positive spatial correlation and spatial spillover effect between high-quality economic development level and carbon emission intensity. Green investment has a U-shaped or N-shaped nonlinear impact on high-quality economic development, and an inverted U-shaped or inverted N-shaped nonlinear impact on carbon emission intensity. At present, it generally shows a trend shifting from restraining high-quality economic development and carbon emission reduction to promoting high-quality economic development and carbon emission reduction. Different types of green investment have obvious heterogeneity in the impact on high-quality economic development and carbon emission intensity. Compared with environmental protection investment and productive green investment, the increase of green enterprise financing is more conducive to high-quality economic development and carbon emission reduction. Carbon emission intensity has a mediating effect, that is, green investment can affect high-quality economic development by affecting carbon emission intensity. On one hand, it is necessary to establish and improve the regional linkage mechanism to effectively use the spatial spillover effects of high-quality economic development and carbon emission reduction; on the other hand, it is necessary to continue to increase the scale and enlarge the scope of green investment, and implement differentiated strategies for all kinds of green investment to improve the quality and efficiency of investment, give full play to the role of green investment in promoting high-quality economic development and carbon emission reduction, and achieve a win-win situation of economic development and environmental improvement.