In the current signal, the weak bearing fault features will be submerged in strong noise and difficult to detect. Therefore, a bearing fault detection approach based on improved variational mode extraction is proposed. All the uncorrelated frequencies will be eliminated, and only the fault feature frequencies can be retained in the proposed approach. A constraint factor adjustment method based on signal equivalent system bandwidth is proposed for the problem that fault features may be decomposed into several modes and weakened. The experimental results show that the proposed approach can effectively extract weak bearing fault features, and only requires a very low amount of computation.