A data storage device includes a memory device and a memory controller. The memory device includes multiple memory blocks. The memory controller determines whether execution of a garbage collection procedure is required according to a number of spare memory blocks. When the execution of the garbage collection procedure is required, the memory controller determines an execution period according to a latest editing status of a plurality of open memory blocks; starts the execution of the garbage collection procedure so as to perform at least a portion of the garbage collection procedure in the execution period; and suspends the execution of the garbage collection procedure when the execution period has expired but the garbage collection procedure is not finished. The memory controller further determines a time interval for continuing the execution of the garbage collection procedure later according to the latest editing status of the open memory blocks.