The invention provides a method of judging low-frequency oscillation type of a power system, comprising: when it is detected that low-frequency oscillation occurs in the power system, acquiring waveform of active power of the power system from an oscillation start phase to a steady state oscillation phase; if the waveform meets a first judging condition, acquiring that the low-frequency oscillation is of forced oscillation type, wherein the first judging condition refers to high-order oscillation frequency component content of the waveform in the steady state oscillation phase is greater thana triangular wave theoretical value. The method has the advantages of high trust level and good judging visuality.