An integrity check method applied to an electronic device includes: fetching at least one portion of external data into a specific memory, where the external data is stored within the electronic device; during fetching the portion of the external data into the specific memory, checking whether the size of the fetched data in the specific memory reaches a predetermined value, where the predetermined value is less than the total size of the external data; and when the size of the fetched data in the specific memory reaches the predetermined value, enabling an integrity check of the fetched data.