An automatic detection technique of nonstationary multiple oscillations in industrial control loops is proposed. The technique is based on an improved wavelet packet transform (WPT) which integrates Shannon Entropy, with a proposed non-Gaussianity test and quasi-intrinsic mode function index to automatically generate the wavelet packet decomposition structure. An optimal frequency resolution of the process data for oscillation detection purposes is obtained in a form of a binary tree. Comparative studies on simulated examples as well as industrial cases indicate that the proposed approach is robust to the nonstationary features of oscillations.