A Quenching & Self Tempering(QST)treatment is one of advanced thermo-mechanically controlled processes to develop high strength and good toughness H shaped beams.However,the QST has sometimes caused their abnormal H shape called “off-squareness” due to non-uniform rapid cooling.In this paper,a correlation between the non-uniform rapid cooling and shape deformation is observed by QST test equipment.In order to understand the mechanism,deformation behaviors are analyzed by a commercial software package,DEFORM,coupled with thermal expansion and volumetric shrinkage during phase transformation in accelerated cooling,its reliability was evaluated with direct measure of deformation.