A method for discovering an application topology relationship provided by this application, in a packet transmission process, API calling information is recorded, and a topology discovery server determines, by analyzing collected API calling information, whether interaction exists between virtual machines in a virtual machine cluster. By using the foregoing analysis manner, the topology discovery server may further determine interaction frequency that is between virtual machines and to which the collected API calling information relates, and determine an application topology relationship between the virtual machines according to the interaction frequency of the virtual machines. The foregoing solution provides a method for discovering an application topology relationship between virtual machines in a virtualization scenario, where an application topology relationship between virtual machines is determined by analyzing API calling information generated in a packet transmission process, and therefore complexity of the solution is relatively low.