A method for monitoring an epicyclic gear train of an aircraft, wherein the epicyclic gear train includes two coaxially mounted first toothed wheels and at least one second toothed wheel meshing with the first two toothed wheels, the method comprising the following steps of: - acquiring, at a predetermined sampling frequency, first values ( S ( t i )) of a signal formed by a progressive mechanical wave generated in the epicyclic gear train, said first values forming primary mechanical wave data; - measuring, at a plurality of successive time instants, values ( V mes_r ( t j )) of a speed of rotation of at least one of the first two toothed wheels and the at least one second toothed wheel , said measured values forming primary rotation data; - from at least the primary mechanical wave data ( S ( t i )), determining second values ( S ( φ k )) of said signal formed by a progressive mechanical wave generated in the epicyclic gear train, said second values corresponding to a regular sampling as a function of the phase and forming secondary mechanical wave data; and - using the secondary mechanical wave data ( S ( φ k )) to detect an anomaly related to the operation of the epicyclic gear train , characterized it further comprises, the following step: - from primary rotation data ( V mes_r ( t j )), calculating values (Vc(tj)) of a rotational speed of a point of contact between the first gear wheel and the second gear wheel of the epicyclic gear train, said calculated values forming secondary rotation data ; and in that secondary mechanical wave data are determined using the primary mechanical wave data ( S ( t i ))) and said secondary rotation data (Vc(tj)), and correspond to regular sampling as a function of the phase of said contact point. - acquiring, at a predetermined sampling frequency, first values ( S ( t i )) of a signal formed by a progressive mechanical wave generated in the epicyclic gear train, said first values forming primary mechanical wave data; - measuring, at a plurality of successive time instants, values ( V mes_r ( t j )) of a speed of rotation of at least one of the first two toothed wheels and the at least one second toothed wheel , said measured values forming primary rotation data; - from at least the primary mechanical wave data ( S ( t i )), determining second values ( S ( φ k )) of said signal formed by a progressive mechanical wave generated in the epicyclic gear train, said second values corresponding to a regular sampling as a function of the phase and forming secondary mechanical wave data; and - using the secondary mechanical wave data ( S ( φ k )) to detect an anomaly related to the operation of the epicyclic gear train , characterized it further comprises, the following step: - from primary rotation data ( V mes_r ( t j )), calculating values (Vc(tj)) of a rotational speed of a point of contact between the first gear wheel and the second gear wheel of the epicyclic gear train, said calculated values forming secondary rotation data ; and in that secondary mechanical wave data are determined using the primary mechanical wave data ( S ( t i ))) and said secondary rotation data (Vc(tj)), and correspond to regular sampling as a function of the phase of said contact point. - from primary rotation data ( V mes_r ( t j )), calculating values (Vc(tj)) of a rotational speed of a point of contact between the first gear wheel and the second gear wheel of the epicyclic gear train, said calculated values forming secondary rotation data ; and in that secondary mechanical wave data are determined using the primary mechanical wave data ( S ( t i ))) and said secondary rotation data (Vc(tj)), and correspond to regular sampling as a function of the phase of said contact point. <EOS>