A memory refresh method is applied to a computer system including a processor, a memory controller, and a dynamic random access memory (DRAM). The memory controller receives a first plurality of access requests from the processor. The memory controller refreshes a first rank in a plurality of ranks at shortened interval set to T/N when a quantity of target ranks to be accessed by the first plurality of access requests is less than a first threshold and a proportion of read requests in the first plurality of access requests or a proportion of write requests in the first plurality of access requests is greater than a second threshold. T is a standard average refresh interval, and N is greater than 1. The memory refresh technology provided in this application can improve performance of the computer system in a memory refresh process.