The agricultural drought vulnerability dynamic assessment is of great significance for the sustainable development of regional agriculture. In order to analyze the development trend of agricultural drought vulnerability evaluation subsystem and indexes, and identify the main indexes that affect the change of regional agricultural drought vulnerability, an adjoint function of connection number, which was the five-element semipartial subtraction set pair potential was constructed. Then, a dynamic evaluation model of regional agricultural drought vulnerability was established, application results of Bengbu City showed that, in the agricultural drought vulnerability evaluation system of Bengbu City, the overall trend of exposure subsystem from 2001 to 2010 was fluctuated between the symmetrical potential and the partial inverse potential, and it was developed towards the reduction of set pair potential. The agricultural drought vulnerability showed an increasing trend, the main index that had a great impact on the vulnerability in Bengbu City was multiple cropping, and it displayed a trend to the inverse potential. Furthermore, the development of damage sensitivity subsystem was fluctuated greatly, from 2001 to 2010, it was gradually developed from the partial inverse potential to the partial identical potential, and the evaluation results showed a positive trend. The decrease of unit added value for agricultural water consumption made an obvious improvement of agricultural drought vulnerability in Bengbu City. Moreover, in 2001—2009, the disaster prevention ability subsystem was in the partial inverse potential. After 2009, it was gradually changed to the symmetrical potential. Meanwhile, the vulnerability showed a slow improvement trend, and the primary influence factors were water-saving irrigation rate and per capita income of farmers. The research provided a scientific decision basis for improving the regional agricultural drought disasters vulnerability, and also provided an effective way to deal with the multi-level problems of complex systems.