An access method for a memory device is provided. The access method includes receiving external data; reading a plurality of first memory cells of the memory device according to a write address to obtain first original data; comparing the external data and the first original data to determine whether the number of specific cells among the first memory cells is higher than a predetermined value, wherein the value of each of the specific cells would be changed from a first value to a second value in response to the external data being written into the first memory cells; and reversing the external data to generate reversed data and writing the reversed data into the first memory cells to replace the first original data in response to the number of specific cells being higher than the predetermined value.