The turnip (Brassica rapa) is a multipurpose crop traditionally utilized for food, fodder, and medicinal materials in China. However, it remains unclear how it adapts to harsh environments in Xizang. To clarify the gap, this study investigates the impact of altitude on the nutritional profile of the “Zhongke 1” turnip across five altitude gradients (3300 m, 3600 m, 4270 m, 4300 m and 4450 m). Comprehensive post-harvest analyses of key nutritional parameters were conducted to evaluate quality variations at different altitudes. The results indicated that both the relative fodder value and relative grass quality of the turnips reached levels comparable to high-quality forage grasses. Additionally, the sugar and soluble carbohydrate content of the turnips exhibited a distinct pattern, initially declining and then rising with altitude. Total digestible nutrients exceeded 60%, while the crude protein content remained above 14% across all elevations. The lignin content in the belowground part of the turnip at 4450 m was more than two times higher than at 3300 m (6.59% vs. 2.96%). Notably, most nutritional indicators remained stable even at the highest elevation of 4450 m, highlighting the strong adaptability of turnips to the diverse environmental conditions of Xizang. The study further identified soil chemical properties, rather than temperature or precipitation, as the primary factors driving nutritional variations across altitudes. In conclusion, the turnip variety showed significant potential as a high-quality and high-productivity forage crop in high-altitude regions more than 4000 m above sea level. This study is of great significance for understanding the altitude adaptability of turnip quality and promoting the development of animal husbandry in the high altitude area of the Xizang Autonomous Region.