The developed software for instable heat transfer calculation in crystallizer of continuous caster for square billet during solidification may be used to predict the temperature distribution in crystallizer and the thickness of billet shell.Due to the existence of longitudinal and transverse and corner air gap the ununiform heat transfer during solification has been considered in the model. Meanwhile

the equivalent specific heat method was introduced to deal with the latent heat on solification front.The temperature distribution in crystallizer and solidified shell thickness were obtained based on the square billet in the Capital iron-steel group company

and the effects of drawing speed on billet temperature and shell thickness were analyzed. The results showed that simulated billet temperature and solidified shell thickness were well in agreement with the pratical results.