A memory access system that includes a data sending apparatus, an optical transmission medium, and a data receiving apparatus. The data sending apparatus includes a signal generator, an optical switch, and an optical modulator. The signal generator controls the optical switch to output the optical wave of the wavelength corresponding to the target memory, and the optical wave carries an electrical signal corresponding to an access request, so that an optical signal carrying the access request is directly transmitted from the optical transmission medium to the data receiving apparatus without passing through the optical switch anymore, which avoids noise interference generated when the optical signal passes through the optical switch.