The invention discloses a second order filter mechanism of a rural power grid de-icing device. The second order filter mechanism consists of a second order inductance filter (1), a second order capacitive filter (2), a harmonic measurement instrument (3), an inductance adjuster (4) and a capacitance adjuster (5), wherein the output end of the second order inductance filter (1) is connected with the input end of the second order capacitive filter (2). The output end of the second order capacitive filter (2) is connected with the input end of the harmonic measurement instrument (3). The output end of the harmonic measurement instrument (3) is connected with the inductance adjuster (4) and the input end of the capacitance adjuster (5) in parallel. The current harmonic distortion on the input side of the rural power grid de-icing device can be effectively suppressed, adjustment of an inductance value and a capacitance value can be automatically implemented, the good smoothing effect is played on current fluctuation on the output side, and adjustment amplitude of the chopped wave frequency of an insulated gate bipolar transistor (IGBT) can be effectively improved in a harmonic permissible range.