To estimate the number of mechanical vibration sources from the convolution mixtures with fewer sensors than sources, a new method combined with EMD-SVD- DE（Empirical Mode Decomposition, EMD; Singular Value Decomposition, SVD; Dominant Eigenvalue, DE）was proposed. The characteristic forms of vibration sources were obtained through the EMD of the mixtures. The relation matrix of the characteristic forms of different mixtures was used to get the eigenvalues of sources which were used to determine the number of sources by means of SVD and DE. It is verified that the new method yields a correct estimate of source number in the simulation and test. It is help to analyze the mechanical vibrations in the fault monitoring system and to separate the useful mechanical vibrations efficiently from the mixtures.