The Tianshan Mountain Northern Slope Economic Belt is the largest economic belt in China, and is undergoing a development focus as part of the Belt and Road Initiative. Green development in this economic belt provides an important reference for other countries along the Belt and Road route. This study assesses the environmental performances of the Tianshan Mountain Northern Slope Economic Belt based on regional and industrial levels. Three wings of this economic belt—the south wing, middle wing, and north wing—are defined using the environmental performance assessment results. The environmental performance of the north wing (which includes the Kuytun–Karamay–Wusu economic zones) is best, followed by that of the south wing (which includes the Gulja–Korgas–Qapqel economic zones, the Urumqi–Changji economic zones, and the Turpan–Kumul economic zones). The environmental performance of the middle wing (which includes the Shihezi–Manas–Shawan economic zones and the Bortala–Jinghe–Alashankou economic zones) ranks lowest. Strategies for the green industrial development of these three wings are suggested based on the assessment results.