A time domain dielectric spectrometer of current type is designed to overcome the shortcomings of the time domain dielectric spectrometer of voltage type and the instrument sensitivity is enhanced.The slow effect of benzene which has not been observed by voltage type spectrometer is obtained with the current type spectrometer.It is found for paraffin that the slow lineshape parameter is smaller than 1/2.The new current type spectrometer is shown to provide an effective and convenient method for detecting the tiny inpurity of hydrocarbon