Sustainability is a strategic choice for the transition to a green economy in China. Improving green total factor energy efficiency (GTFEE) is the key to realizing the dual targets of energy saving and economic growth. This paper assesses the nonlinear influence of environmental regulation (ER) on technical innovation (TI) affecting GTFEE by establishing a dynamic panel threshold model using panel data of 271 prefecture-level cities in China from 2004–2016. Meanwhile, a system GMM approach is used to verify the channels through which TI affects GTFEE. Finally, the spatial and temporal characteristics of TI affecting GTFEE are analyzed from the perspective of ER. The empirical results are as follows: (1) TI can significantly improve GTFEE, and there is a threshold characteristic of this improvement effect, when ER is above the threshold value, TI has a greater improvement effect on GTFEE. (2) Besides directly influencing GTFEE through green technical innovation effect, TI can also indirectly influence GTFEE via channels such as economic growth effect, industrial structure upgrading effect and foreign investment effect, and the indirect influence channels show ER heterogeneity. (3) The number of cities crossing the threshold of ER in China increases year by year, which helps TI play a role in improving GTFEE, but there are still a small number of cities that do not cross the threshold during the sample period, which should attract the attention of local governments.