The current transformer (CT) transient saturation easily leads to the misoperation of differential protection. The P-class, PR-class and TPY-class CTs which are widely used on site show different transient characteristics. For these three types, industrial practical CTs are selected, experimental test and mathematical fitting are carried out to get the relevant parameters and then obtain the mathematical expression of core flux. Whether the CT is saturated or not and when the CT get into saturation can acquired by comparing the expression with the measured saturation flux. Three types of industrial practical CTs are used to carry out dynamic simulation tests for single short circuit, reclosing in the permanent fault, conversion fault and magnetizing current. Their transient saturation characteristics are analyzed. On the basis of theoretical analysis and dynamic tests, the methods for CT transient saturation and the CT selection scheme are discussed. This work is supported by Science & Technology Project of State Grid Hubei Electric Power Company (2017, No.1).