With the continuous development of information technology, smart meters have been widely deployed in many households, allowing power companies to better identify the socio-demographic characteristics of power consumers and provide diversified services. However, one of the threats faced by smart grids is energy theft, particularly through False Data Injection Attacks (FDIA), which tamper with meter data for covert theft, posing a serious threat to the safe and stable operation of power systems. To address this issue, an FDIA detection model based on LightGBM was proposed. Normal user electricity consumption data was selected, and different types of FDIA were implemented on some users. Features were extracted using a sliding window method, and the LightGBM model was employed for multi-class detection. Experimental results showed that this model excelled in detection accuracy and real-time performance, accurately identifying different types of FDIA with quick and efficient detection, meeting the real-time requirements of practical applications. This model could help ensure the safe operation of power systems.