A method and a terminal device for keeping a subscriber identity module card in a standby state are provided. The method for keeping a subscriber identity module card in a standby state includes receiving, by a terminal device, an enabling request, where the enabling request is used for requesting simultaneous standby of a first subscriber identity module card and a second subscriber identity module card; invoking a third-party invocation interface provided by an operating system of the terminal device; performing interaction with a subscriber identity module card control module, so as to complete a network access process of the first subscriber identity module card on the basis of a data file of the first subscriber identity module card; and keeping the first subscriber identity module card and the second subscriber identity module card in a standby state at the same time according to the enabling request.