A memory data migration method, apparatus, and system are provided. During memory migration, data is classified into two parts based on a hot and cold degree of the data. Hot data is directly migrated, and cold data is written into a shared storage device shared by memories. When needing to be used in a destination-end memory, the cold data may be read from the shared storage device. This reduces an amount of data that needs to be migrated to the destination-end memory, thereby improving memory migration efficiency.