A method of and an apparatus for controlling a data storage system according to a temperature which thermally expands a write head pole tip of a write head includes supplying the write head with a predetermined warming current in a low temperature environment, so as to prevent a degradation of a writing characteristic of a signal in an initial writing stage. Therefore, errors due to a degradation of a signal level written in a sector of an initial writing mode do not occur by performing a warming write using the predetermined warming current so that data existing in a storage system before performing a writing mode is not erased, and by sufficiently thermally expanding the write head pole tip of the write head until a saturation state before writing starts.