Vulnerability of agriculture is mainly determined by the sensitivity of farmland productivity to climatic changes. The global climate is predicted to continue its warming trend with increases in some extreme events in the future, which will have a great impact on crop yield, and seriously threaten regional food security. The scientific assessment of farmland productivity vulnerability and analysis of climate impact mechanisms, are helpful for mitigating climate change in pact and ensuring regional food security, which has great practical and scientific implications. Based on the normalised vegetation index of satellite remote sensing data from 1982 to 2015, this paper takes the "Bangladesh, China, India and Myanmar Economic Corridor" in the "Belt and Road" region as the study area, and the sensitivity, adaptability and vulnerability indexes of farmland productivity to climate change (as defined by the IPCC), were calculated for the concepts of interannual variability and its changing trend. Changes in the spatial pattern of farmland ecosystem vulnerability, and analysis of climate impact mechanisms in the study area were carried out for different time periods. The results showed that:(1) Compared with 1982-2000, the vulnerability of farmland in the study area increased in 2000-2015, the extent of the high and exceedingly vulnerable area expanded by 0.42% and 1.12% respectively, and their spatial distributions moved northward; (2) Linear regression analysis between annual precipitation, annual average temperature, annual radiation and annual accumulated NDVI, showed that the area influenced significantly by climate increased by 21.3% and 16.7% in Bangladesh and Myanmar respectively, relative to their total national farmland areas, while the area in India decreased by 10.5%, and in the whole study area it decreased by 8.1%; (3) The multiple correlation coefficient (R²) of the linear regression equation is indicative of the variability that is attributable to climate change, and it increased in the overall study area by 12%, with India's climatic contribution increasing from 48% to 64%, an increase of 16%; (4) The impacts were chariacterized with a slight decreasing of its scope but an increasing of its degree, and there are large regional differences; high temperatures, droughts and floods caused by uneven seasonal precipitation are key climatic factors contributing to the high vulnerability of farmland. This study not only mapped the vulnerability, but also revealed its changes and impacts from climate change over the 34 years, providing methods and insights for agricultural adaptation management and policy-making in those countries, and for consideration of regional food security in "The Belt and Road Initiative".