Embodiments of this application disclose a service type determining method and a related device. A first device obtains a dataset, where the dataset includes at least two 5-tuples. The first device determines a target feature (the target feature is used to indicate a service type corresponding to a target triplet) corresponding to the target triplet based on the dataset. In this way, the first device can identify the service type corresponding to the target triplet based on the target feature, to facilitate operations such as packet transmission traffic control or application identification based on the importance indicated by the service type.