A nonlinear and non-stationary phenomenon is often generated for the loose fault signal of the bolt. In this paper, the bolt loose state recognition method based on the combination of VMD (Variational Mode Decomposition) and LSSVM (Least squares support vector machine) is proposed. The bolt loose test platform is used to collect the vibration signals of the loose state of the bolts under the four working conditions. The vibration signal of each working condition of the bolt loose state is decomposed by using the VMD. The energy entropy of each modal component by the VMD is calculated. The energy entropy of each modal component decomposed by VMD is as a feature structure eigenvector matrix, which is trained and state-recognized by VMD-LSSVM. The experimental results show that the method can effectively identify the loose state of the bolt loosening state, and the VMD-LSSVM has a better performance in states recognition compared with the EMD-LSSVM model.