Abstract:A modified ensemble empirical mode decomposition (MEEMD) is proposed in this paper, and its basic principles are discussed. The numerical simulation shows that MEEMD is a better adaptive signal decomposed method, which not only restrains the disadvantage of mode mixing problem of the EMD method, but also overcomes the non-IMFs, mode splitting and noise residue problems. The MEEMD method is then used to analyze the vibration signal of the block of a diesel engine. The analysis achievements show that the mechanical shock component originating from piston-slap could be successfully separated from the combustion shock component, and the dominate vibration sources could be obtained.