Gynaephora menyuanensis, an endemic species of the Qinghai-Tibet Plateau, has been extensively researched because of the significant damage that they cause to grasslands. However, as a result of their adaptation to the plateau, this species could be regarded as a model organism to explore the response of herbivores to extreme environments and climate change. To explore the effect of global warming on this species, we conducted a simulated warming trial by using open top chambers (OTCs) at the Haibei Alpine Meadow Ecosystem Research Station, Northwest Institute of Plateau Biology of Chinese Academy of Science. To simulate different warming levels, we adopted four OTCs of different calibers and five replications of each size (20 OTCs in total). The temperature of each OTC was recorded using a HOBO thermograph. From April to September 2014, 10 G. menyuanensis larvae finishing diapause were maintained under casings (35 cm×25 cm×40 cm) of thin wire, and the length, weight, survival, and width of the head capsule were measured every seven days. G. menyuanensis instar larvae were estimated based on their head width. The results showed the following: higher warming amplitudes resulted in earlier first instar larval activity and pupal development after overwintering, and shorter caterpillar larvae development durations with temperatures from +0℃ (ambient temperature) to +1.26℃; warming enhanced the relative growth rate of caterpillar larvae and advanced the peak of its development to May; higher temperature elevations resulted in lower weights of caterpillar larvae; and temperatures from +0 to +1.26℃ enhanced the survival rate of larvae, but increased temperature to +1.98℃ reduced it. Therefore, we concluded that there was a range of elevated temperatures positively affecting G. menyuanensis larvae and enhancing their adaptation to the grassland. However, when the temperature or the warming rate exceeded this range, G. menyuanensis larvae could not adapt to the change, but the response of grasses to G. menyuanensis larvae under these warming conditions is still unknown. There were two innovations in this article: First, we explored the response of herbivore insects to different warming levels in the Qinghai-Tibet Plateau by focusing on G. menyuanensis. Second, we improved the traditional OTC to simulate different elevated temperatures.