In response to the problem that the traditional capacitive road covering detection method has weak identification ability and low discrimination at low temperatures，the dielectric loss and relaxation phenomena of capacitors and covers are studied based on the series equivalent model of the capacitor and starting from the principle of dielectric polarization. The effects of covers and detection frequency on the equivalent series capacitance and equivalent series resistance of the capacitor was analyzed and a capacitor high-pass filter circuit was designed and built. By comparing the amplitude attenuation ratio and phase difference between the output and input signals of the high pass filtering circuit, the changes in equivalent series capacitance and equivalent series resistance of capacitors can be indirectly measured to achieve the identification of the type of covering material. The sample was tested in the incubator. The experimental results show that when the temperature is between 10 ℃ and 60 ℃, the phase difference during drying is greater than 30°, and the decay ratio is less than 0.8. The phase difference is less than 10°, and the decay ratio is close to 1. When the temperature is between -30 ℃ and 0 ℃, the decay ratio of dry, freezing and snow cover is crossed. The phase difference varies slowly with temperature, with an average phase difference of more than 40° when dry, less than 30° when frozen, and somewhere in between when covered with snow. The neural network classification model is constructed by using temperature, phase difference and decay ratio, which is deployed to the single chip computer and measured. Measured data show that the method achieves an accuracy of 95% in distinguishing between dry and stagnant water between 0 ℃ and 60 ℃, and the accuracy of distinguishing between dry, frozen, and snow cover is about 83% in the range of -30℃ and 0℃, which can meet the needs of road covering detection.