The non synchronous sampling and field noise have great influence on the accuracy of the dielectric loss tangent, for which a new method for measuring dielectric loss angle (DLA) based on iterative sparse decomposition is proposed in this paper. To improve the calculation accuracy of the dielectric loss angle, the input signal can be expressed as the signal component and form of a small amount of signal, and then the fundamental phase is obtained by matching the optimal atom with the signal wave. In the situations of fundamental frequency fluctuation, real value of DLA variance, changing of harmonic component and white noise influence, the DLA measurement results were obtained through simulation experiments by the method proposed in this paper, and the DLA results were calculated by Blackman self-convolution window(BSCW) and triple-spectrum-line interpolation and Higher-order sine fitting algorithm with Hanning-windowed interpolated. The results show that the DLA measurement method presented in this paper has a better accuracy and overcoming the shortage of spectrum leakage and fence effect.
