Abstract: With the rapid industrialization and urbanization in eastern China, urban ecological security (UES) pattern was gaining attentions in the typical geographical region, with the high climatic sensitivity, biological diversity and environmental complexity, especially in the China’s north-south transitional zone. In this paper, based on land cover type and social statistics datas for the period of 2008-2017, the spatiotemporal variation of the UES pattern was analyzed in north and south of Qinling-Huaihe region. More importantly, the obstacle degree model was introduced to explore the influencing factors of the UES in China’s north-south transitional zone. The results showed, (1) Between 2008 and 2017, the UES grade in the study area was being a critical risk level and showed a slight increase with a linear tendency being 0.003%/10a. That implied the UES tended to be better and stable; (2) The spatial pattern of UES in north and south of Qinling-Huaihe region presented the east was higher than the west, while the UES index in the south area is higher than that in north area. In detail, high value of UES was mainly distributed in the middle and lower reaches of the Yangtze River and the east of the Huaihe Plain; (3) In the aspect of future tendency, the characteristics of the spatial pattern evolution of UES shown that about 24.2% of the study area experienced the increasing trend, which was continuously concentrated in Yangtze River Delta and Jianghan Plain. The areas with UES decreasing mainly distributed in Guanzhong Plain and the west of the lower reach of the Yellow River, accounting for about 35.2%; (4) In terms of influencing factors, the main factors affecting UES had consistency in different areas of China’s north-south transitional zone and they were water and wetland coverage, per capita green area, total water resources and proportion of tertiary industry. It can be effective to improve the UES by means of industrial structure optimization, increasing the proportion of ecological land and guaranteeing the total resource security.