A trusted application running method applied to a computer system on which a trusted execution environment (TEE) and a rich execution environment (REE) are deployed, where one or more trusted applications (TAs) run on the TEE operating system. The TEE operating system may start a target TA. Then, the target TA may send, to the TEE operating system, a loading request for a target dynamic library supporting the target service. The TEE operating system may load the target dynamic library to memory space of the target TA in response to the loading request. In this way, before the target TA runs the target service, a program module used to support the target service does not need to be loaded to the memory space of the TA, thereby reducing a waste of the memory space of the TA.