False data injection attacks (FDIAs) have recently become a major threat to smart grids. Most of the existing FDIA detection methods have focused on modeling the temporal relationship of time-series measurement data but have paid less attention to the spatial relationship between bus/line measurement data and have failed to consider the relationship between subgrids. To address these issues, in this article, we propose a subgrid-oriented microservice framework by integrating a well-designed spatial-temporal neural network for FDIA detection in ac-model power systems. First, a well-designed neural network is developed to model the spatial-temporal relationship of bus/line measurements for subgrids. A microservice-based supervising network is then proposed for integrating the representation features obtained from subgrids for the collaborative detection of FDIAs. To evaluate the proposed framework, three types of FDIA datasets are generated based on a public benchmark power grid. Case studies on the FDIA datasets show that our method outperforms state-of-the-art methods for FDIA detection in these datasets.