Abstract: With the development of power grid facilities, the problem of low-frequency noise from substation has been paid more and more attention. In order to analyze the applicability of low-frequency noise control index at the boundaries of 500 kV substations, the low-frequency noise data acquired at the boundaries of nine substations are analyzed. Besides, two substations are selected to compare the noises above and below the actual wall at the factory boundary and near the main transformer before and after the noise reduction measures respectively. The results show that the peak value in the 1/3 octave band with center frequency of 100 Hz is most obvious; the average value of lowfrequency sound energy proportion (θ_low) of noise samples at substation boundaries is 87.2%, and the average value of the difference between equivalent continuous C-weighted sound pressure level and equivalent continuous A-weighted sound pressure level (L_Ceq-L_Aeq) is 11.0 dB. Generally, the samples with lower L_Aeq have higher θ_low and L_Ceq-L_Aeq; the L_Aeq and L_{100 Hz} of boundary noise below the wall are usually lower than that above the wall, but the θ_low and L_Ceq-L_Aeq below the wall might be higher. After adopting the noise control measures, L_Aeq and sound pressure level of 1/3 octave band with center frequency of 100 Hz (L_{100 Hz}) of boundary noise could be effectively controlled, but θ_low and L_Ceq-L_Aeq might be higher than before. Thus, it is not reasonable to directly introduce θ_low and L_Ceq-L_Aeq to evaluate the lowfrequency noise at the boundaries of substations. The analysis results can provide a reference for the selection of available control indices and the determination of low-frequency noise limit at substation boundary.