To optimize the layout of the outbound transportation system and enhance system resilience, a "Sensitivity-Response" dual-dimensional evaluation index system was constructed. The comprehensive methods including set pair analysis, spatial Markov chain, and obstacle degree model were used to analyze the dynamic characteristics and driving mechanisms of vulnerability in 225 inland cities in China. The findings reveal that vulnerability demonstrates significant multi-polarization and spatial club convergence. The overall vulnerability decreases annually, evolving from bi-polarization to multi-polarization, with a reduction of absolute difference. Vulnerability exhibits significant spatial auto-correlation and spillover effects, forming a spatial pattern where "high-vulnerability is clustered along the borders, while low-vulnerability diffuses from urban agglomerations". A low-vulnerability neighborhood environment increases the probability of a city's vulnerability transferring downward by 64.5%. The obstructive effects of both freight turnover volume and total import-export trade value weaken annually. In contrast, the hindering effect of shortest inland-port road travel time shifts from a relatively stable to a consistent increase. Furthermore, city hub level and connectivity impose significant constraints on vulnerability of non-hub cities.