A data access system and a data access method achieving effects of power saving and access synchronization during data access are provided. The data access system includes a data processing unit, a bridge device and a memory device. The data processing unit sends an access request signal to initiate data access of at least one unit data. The access of unit data is completed within a plurality of clock cycles of a reference clock signal. The bridge device generates an access signal according to the access request signal, the reference clock signal and a leading time. A pulse of the access signal is determined by the leading time within the clock cycles. The memory device executes the access of the unit data according to the access signal.