This method for analyzing the respiratory activity of a patient comprises the steps (20) for acquiring at least one respiratory activity signal comprising at least one elementary signal corresponding to a respiratory cycle, the general form of which may be expressed by x(t)=x0+x1 cos (Phi(t)), wherein Phi(t) is the phase of said elementary signal, and for analyzing (24, 26, 28) said respiratory activity signal. This analysis (24, 26, 28) comprising steps (24) for extracting, from said respiratory activity signal, said elementary signal, for determining (26) an expression of a phase equation F ( Phi ) = Phi t of said elementary signal and for determining (26) an expression of the phase Phi(t) of said elementary signal as a function of parameters measuring the anharmonicity of said elementary signal and its morphology, from pcosn and psinn functions defined by: p cos n ( t , r ) = &sum k = 1 &infin cos ( kt ) r k k n and p sin n ( t , r ) = &sum k = 1 &infin sin ( kt ) r r k k n .
