The invention discloses a subharmonic detection method based on cascade delay signal elimination method, comprising steps of obtaining a,b,c three-phase voltage signals of a power grid load terminal through a voltage sensor and a digital regulation circuit, utilizing a Clark transform to obtain a voltage signal under two-phase static coordinate system vabc=[va,vb,vc], (2) performing filtering process based on the delay signal elimination on the V alpha Beta which is obtained through transformation to obtain voltage signals which only contains odd- number harmonic component and voltage signal which only contains the even-number harmonic component, (3) performing filtering processing based on the cascade delay signal elimination on the voltage signals which only contain the odd-number harmonic wave component and the voltage signals which only contain the even-number harmonic component to obtain the components of positive sequence and negative sequence of any subharnonic, and (4) performing superposition on the harmonic components to obtain a total harmonic signal. The invention is high in detection accuracy and high a practicability.