An operation method of a memory includes the following steps: determining the number of memory units required to update the content stored therein when the memory is performing a program operation based on the N-bit input data and accordingly generate a first determination result; and providing (N−M) number of loads to a source line decoder of the memory if the first determination result indicates that there are M number of memory units required to update the content stored therein, and thereby coupling the (N−M) number of the provided loads to a transmission path of a power supply voltage in parallel, wherein N and M are natural numbers. A memory is also provided.