Plasma electromagnetic parameters are very important in development of plasma technology. In this paper, a testing method is presented based on a one-dimensional microwave photonic crystal with the cold plasma under test as a defective layer. The transfer matrix method (TMM) is used to simulate the relationship among plasma parameters, frequency offset of the defective peak, and the peak transmission intensity. The results indicate that the plasma and collision frequencies can be mapped into the frequency offset of the defective peak and the peak transmission intensity. Therefore, one can obtain the plasma electromagnetic parameter frequency by measuring the offset of the defective peak and the peak transmission intensity. This measuring approach provides a noncontact and sensitive way of sensing the electromagnetic parameters of cold plasma.