Abstract: The crack morphology and element segregation in continuous casting slabs were studied to solve the problem of internal cracks. The stress of the solidification front was analyzed by a finite element model at a series of reduction parameters and compared with the critical value. It is found that C,P and S enrich in dendrites and exist in grain boundaries,these are just the internal causes,but the true cause for internal cracks is the tensile stress of the solidification front. When the slab passes through the straightening segment,the reduction effect of rollers results in the stress of the solidification front exceeding the critical value,however,the corresponding stresses in the arc and horizontal segments do not exceed the critical value,so the solidification front in the straightening segment would be much easy to crack. Statistics analysis shows that when soft reduction and straightening are separately carried out,the occurrence rate of internal cracks reduces by about 41.3%.