Since the traditional electromagnetic detection technique can not be effectively used to defect the detection for workpiece in the complicated environment, the active electromagnetic detection technique could take the initiative to adjust the device according to the thickness of workpiece and it was presented in this paper. The key point of this research was focused on the measurement method for workpiece with different thickness by designing the active electromagnetic detection for the device. Based on transmissiontype eddy current detection technique, the model of thickness measurement of workpiece was established and analyzed. Furthermore, the experimental platform was set up to conduct the measurement experiments with two groups of thickness. Through the comparisons between the experimental results and the theoretical analysis, it was found that the errors of experimental detection of these two groups are 0.76% and 1.46%, respectively. It could be safely concluded that the proposed model in this paper is feasible to measure the thickness of workpiece by using transmissiontype eddy current detection.