A data storage system with power backup mechanism includes a storage server, N pieces of power supply modules, a plurality of programmable logic devices and a control module. The storage server consumes M units of power in operation, and supports a storage bridge bay standard. The power supply modules respectively generate power for the storage server and a set of power-related signals, wherein the maximum power output of each of the power supply modules is equal to M/N−1 units. The programmable logic devices convert the power-related signals from the power supply modules to two sets of power condition signals. The control module monitors a power condition according to the power condition signals, thereby determining a power health condition of the storage server.