Due to its huge differences in longitude, latitude, and elevation, the transition zone between the second and third steps provides a unique natural profile for basic environmental research on physical geography and human settlements in mainland China. In terrain transition zone, the topographic and marginal effects of vegetation, and their responses to latitude and climate change will provide a geographical reference for in-depth understanding of the ecological pattern and resource endowment of mountainous areas in China. Based on the GIMMS NDVI3g v1 dataset, annual mean temperature and precipitation data from 1982 to 2015, combined with the maximum value synthesis, trend analysis, mutation analysis, variation analysis, and correlation analysis, this paper reveals the spatiotemporal variation trend and response characteristics to climate change of vegetation phenology in terrain transition zone of "plain-mountain" near the north-south direction between the second and third steps of China. The results show that:(1) The terrain transition zone is a periodical vegetation phenological characteristic region which spans the low-latitude region with three crops a year, the mid-latitude region with two crops a year, and the periodic vegetation phenology zone in the high-latitude region with one crop a year; (2) During 34 years, the inter-annual NDVI showed an increasing trend, of which the vegetation improvement area accounted for 58.84%; the inner-annual analysis showed that the vegetation growth period (LOS) change rate of the terrain transition zone was -3.16 d per latitude; (3) The annual average temperature of the terrain transition zone in the 34 years showed an increasing trend with an increase rate from 0.098℃ to 0.386℃ per 10 a, while the annual average precipitation showed a decreasing trend with a decrease rate from 8.29 mm to 31.82 mm per 10 a; (4) The NDVI variation coefficient analysis showed that low volatility change area and relatively low volatility change area accounted for 95.52%, presenting a stable and positive trend; (5) The correlation between NDVI and annual mean temperature decreased as latitude increased, indicating that southern vegetation was sensitive to temperature changes; while the correlation between NDVI and annual mean precipitation increased as latitude increased, indicating that northern vegetation was sensitive to precipitation changes. Vegetation distribution and climate change in terrain transition zone of "plain-mountain" have topographic effects; In the mountain-plain junction zone, due to the human-land conflict caused by urban expansion, the vegetation distribution around the city has a marginal effect.