Abstract: Continuous cooling transformation of three kinds of C and Cr components of high weathering hot rolled H-beam steels were tested with Gleeble-3500 thermal simulation machine to study the influence of cooling rate on microstructure and micro-hardness. The results show that the area of ferrite transformation region of the tested steel with lower Cr content is larger, and that with higher Cr content is smaller. When the content of C and Cr is high, the area of bainite transformation region is smaller, the kinetic process of bainite transformation is changed by a certain proportion of C and Cr elements, which increases the transition period and slows down the growth rate. When the mass fraction of C is lower than 0.02%, within the region of test cooling rate, no martensitic transformation occurrs. The tested steel with low carbon and high chromium composition system has lower sensitivity to cooling, when the cooling rate is within 5℃/s, its performance meets the requirements.