A repairable semiconductor memory device including a memory cell array having a first block to store first system data and a second block to store second system data identical to the first system data. A controller transmits the first system data to a memory unit in response to a reset signal output from a host and the second system data to the memory unit based on a fail detection signal generated by an ECC detection block. The ECC detection block determines whether the first system data is defective. When a defect is generated in the first system data during resetting of the semiconductor memory device, the first system data is repaired by supplying the second system data.