The invention discloses a method for judging a fault section of a multi-terminal DC transmission system based on polar wave energy. The method comprises the steps of: recording a fault start moment, acquiring electrical quantities in time segments before and after the fault start moment, and calculating aerial mode components of a voltage and a current at a protection installation part by utilizing the electrical quantities; calculating a polar wave value of each sampling point at a designated moment at the protection installation part in the time segments according to the aerial mode components of the voltage and the current; extracting a polar wave wavelet coefficient of each sampling point at an arbitrary layer in the time segments, and calculating polar wave wavelet coefficient energy;acquiring the maximum value of the polar wave wavelet coefficient energy at the protection installation part in the time segments, regarding the maximum value of the polar wave wavelet coefficient energy as a reference sampling point, taking at least one sampling point after the reference sampling point, and calculating a sum of the polar wave wavelet coefficient energy of the reference samplingpoint and the at least one sampling point; and judging the sum of the polar wave wavelet coefficient energy, and determining the fault section as an intra-cell fault if the sum of the polar wave wavelet coefficient energy is greater than a setting value set in advance.