The dilatometry curves and the critical phase transformation temperatures of high strength low-alloyed (HSLA) cold rolled sheet steel were determined by thermal simulation test machine. The samples were austenitized at 900°C,deformed at 40% of deformation and cooled at different rates of 0.1°C/s~ 60°C/s. The continuous cooling transformation (CCT) diagram under deformation condition can be drawn. The results showed that the critical phase transformation temperatures are as follows: Ac3=900°C, Ac1=735°C, Ar3=825°C, Ar1=695°C. A few amount of martensite in high strength low-alloyed cold rolled steel can be obtained at the cooling rate of 60°C/s. The experimental data provide the technical references for rolling control, cooling control and heat treatment in real production.