A bidirectional forwarding detection (BFD) method, apparatus, and system, where when a first virtual machine receives BFD packets from a second virtual machine, prediction duration and a predetermined quantity of sample time intervals are obtained. An eigenvalue is obtained according to the prediction duration and the predetermined quantity of sample time intervals, where the eigenvalue indicates a possibility of fault occurrence on an application in the second virtual machine. For an application that is running on the second virtual machine, the eigenvalue is compared with a preset fault determining criterion of the application, and whether the application is faulty is determined according to a comparison result.