The invention provides a method for extracting a narrow bandwidth signal based on a harmonic wavelet packet. The method comprises the following steps: collecting a noise signal as a data sample x(t) for extracting the narrow bandwidth signal; carrying out FFT transform x(omega) on the acquired data sample; performing frequency domain transformation on the harmonic wavelet packet to determine a frequency parameter m = 2j and n = 2j + 1 of the narrow bandwidth signal according to a harmonic wavelet packet frequency domain model; carrying out convolution operation on the sample data x (omega) andthe harmonic wavelet packets psi(omega) to obtain frequency domain narrow bandwidth signals Wx(m, n, omega)=x(omega)*psi(omega); and performing IFFT transform on Wx(m, n, omega)=x(omega)*psi(omega) to obtain the extracted time domain signal. The method is particularly suitable for extracting weak signals of a certain frequency or a certain narrow bandwidth frequency band fromstrong noise, and has the advantages of small extracted signal distortion, high precision and high operation speed.