Abstract: The influencing factors on triangular zone cracks were obtained by analyzing the database of sulphur printing results of continuously cast slabs. The result indicates that triangular zone cracks get worse with the increasing of sulpher content, superheat, casting speed and width of the slab. On the basis of that, the responding control principles were proposed as follows. The content of carbon should be near to the lower limit 0.13%. When the content of sulphur is between 0.015% and 0.020%, the content of manganese should be between 0.375% and 0.50% to assure the ratio of manganese to sulphur is above 25. The superheat of steel in tundish should be below 25 ℃ and the casting speed below 1.3 m/min. It is very necessary to improve the intensity of secondary cooling in the narrow side of a wider slab and ansure the precision of continuously cast machine.