Urban expansion is a key factor that affects the regional ecological environment, therefore, clarifying the relationship between urban expansion and ecological risk is of great and practical significance for sustainable urban development and ecological environment optimization. However, current research remains relatively limited in elucidating the relationship between urban expansion and ecological risk from a micro-scale perspective, especially regarding the impact of different urban development modes on landscape ecological risk. The multi-order adjacency index (MAI) is a novel method for quantifying urban expansion landscapes at more microscopic spatial scales. It uses multi-order buffer zones to distinguish relationships between new and original urban land uses, effectively revealing the processes and characteristics of micro-level urban expansion. Taking Jiangsu Province as a case study, this paper proposes an MAI algorithm based on a grid data model to identify urban expansion patterns, constructs a landscape ecological risk model to reveal the long-term evolution characteristics of environmental risks, and uses Pearson correlation analysis to evaluate the evolution and relationship between urban expansion patterns and landscape ecological risks. The results show that: (1) The urban scale of Jiangsu Province exhibited a expansion trend, and the gravity center of expansion showed a staged evolution pattern of "Northern Jiangsu (1985-2000) → Central Jiangsu (2000-2010) → Southern Jiangsu (2010-2020)", with fringe urban expansion being the dominant pattern. (2) Landscape ecological risk generally showed a fluctuating trend of "rising-declining-recovering", and the landscape ecological risk level in Southern Jiangsu, Central Jiangsu, and the eastern coastal area was significantly higher than other regions, with the intense trend of risk level transfer in Northern, Central, and Southern Jiangsu consistent with urban expansion. (3) The landscape ecological risk index was positively correlated with the MAI value, with the intensity of the impact of urban expansion patterns on ecological risk within the same unit area ranked as infill