The Huanghuaihai Plain is one of the most important agricultural landscape areas in China. The division of plant functional groups is conducive to the cognition of ecosystem structure, functions, and services, so as to better understand the status and role of the remaining non-agricultural habitats in the agricultural landscape in regional biodiversity conservation and ecosystem services. In a typical area of the Huanghuaihai Plain, the plant communities in the main non-agricultural habitats (forestland, hedges, field roads, ditches) were investigated. Based on the classification results, the characteristics of plant functional groups in each habitat and their contribution to ecosystem services were discussed. The results showed that (1) in terms of species richness, dicots were dominant, while monocots were less frequent in each habitat but had a higher community status. Species richness and important values of annual and perennial plants were basically the same. (2) From the perspective of habitat categories, annuals and monocots were more dominant in habitats such as field roads and hedges. With less human disturbance, a large number of perennial species start to appear in forest land and ditch habitats, although these species mostly appear only occasionally. (3) The common species are annual dicots, with few species but high community status, and there are a large number of occasional perennial dicot species. Further analysis shows that in the agricultural landscape of Huanghuaihai Plain, most of the non-agricultural habitats are in the early stage of community succession, and the main body of the community is composed of annual and monocot functional groups. The community structure is simple, and the dominant population is clear. With the decrease of disturbance intensity, the perennial and dicot species in the forest and ditch habitats appear in large numbers, and the occasional species increase, while the dominant species declines. From the perspective of comprehensive consideration of species diversity conservation and ecosystem services provision, although these non-agricultural habitats play an important role, their role is still limited. In the future, it is still necessary to further reduce the interference of human activities on non-agricultural habitats, so as to further improving the overall level of regional ecosystem services.