A method for service discovery in a neighbor awareness network (NAN), and a terminal device, where the method includes receiving, by a first device, a first service discovery message sent by a second device, where the first service discovery message carries service identifier information and first path information, and the first path information includes identifier information of the service initiating device, or identifier information of the second device and the service initiating device, determining, by the first device, second path information according to the first path information, where the second path information includes the identifier information of the service initiating device and identifier information of the first device, and sending, by the first device, a second service discovery message, where the second service discovery message carries the service identifier information and the second path information.