The invention discloses a dielectric loss angle method for reducing the error of a base wave phase algorithm based on model reference self-adaption. According to the dielectric loss angle method, a model reference self-adaption method is adopted, a Levenberg-Marquardt algorithm model is used as a reference model, a base wave phase separation model is used as an adjustable model, and the differencevalue of output of the reference model and output of the adjustable model is used as input of a self-adaption link; a self-adaption algorithm modifies parameters of the adjustable model so that the output state can rapidly and stably approach to tan theta, that is output of the adjustable model approaches to the reference model, wherein the output state is shown in the description. Based on the model reference self-adaption method, the dielectric loss angle method reduces the error generated by synchronous sampling of the base wave phase algorithm.