The macroexamination and micro-examination of the characteristics of the common cavity defect in cold rolled sheet of low carbon Al-killed steel were carried out. The results obtained show the cavity defects are divided into three types. The cavity formed due to normal tensile crack is related to the inclusion in the basis sheet. while the spalls from the basis material or the foreign matter are forced into the basis sheet,the scar and pit type cavities are formed.The rest is related to rolling process.