An ultra-performance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS) method was employed to efficiently and rapidly analyze the chemical composition of steroidal alkaloids in Fritillaria ussuriensis Maxim (FM). The integration of nitrogen rule and improved mass defect filtering eliminated 84.61% of interfering MS1 peaks and facilitated subtype classification. Subsequently, six diagnostic product ions (DPIs) for Fritillaria alkaloids were summarized, guiding structural identification. Additionally, the adoption of molecular networks to infer potential compounds forms a new four-step comprehensive strategy for systematic screening and identification of Fritillaria alkaloids. By screening with the MDF window constructed from the Fritillaria alkaloids MS database combined with the nitrogen rule, a significant number of interfering MS1 peaks were eliminated, and different subtypes were distinguished. In FM, the number of positive-mode MS1 peaks was reduced by 84.61% (from 8,728 to 1,343). By summarizing the fragmentation behaviors of 22 reference standards, the fragmentation pathways and DPIs of five types of steroidal alkaloids were confirmed, providing the first evidence for DPIs of cevanine-seven-membered type Fritillaria alkaloids. Structural confirmation of MS1 peaks was carried out using an in-house database and DPIs. Furthermore, a feature-based molecular network (FBMN) was employed to cluster similar compounds into network clusters for rapid classification and to infer potential steroidal alkaloids using known compounds. A total of 103 Fritillaria alkaloids (65 cevanine type, 7 cevanine-seven-membered type, 18 jervine type, 5 veratramine type, 5 secosolanidine type, and 3 solanidine type) were identified, including 4 potential new compounds and 20 compounds that have been identified for the first time. This innovative comprehensive strategy, which includes NRF, improved MDF, DPIs, and FBMN, can be applied to rapidly screen, classify components, and conduct comprehensive characterization of complex samples such as herbal medicines.