A time domain signal analysis method is provided. The signal analysis method includes the following steps. A signal to be analyzed is received. The signal to be analyzed is iteratively sifted by using Empirical Mode Decomposition (EMD) to extract at least one intrinsic function (IMF). A normalized Hilbert transform is performed on the IMF. The transformed IMF includes phase information. The transformed IMF is processed by means of phase processing to obtain the processed IMF including angular frequency information. The foregoing signal analysis method could be utilized in an ultrasound imaging system to identify image information of ultrasound images.