A compensation method based on reference deconvolution is developed to obtain high-resolution NMR spectra under an unstable magnetic field. It is shown that the applicability of the original deconvolution method is limited for small fluctuation, and a process what may be called phase reconstruction is proposed to compensate large field fluctuation. We demonstrate the method using a probe with a coil that can generate a fluctuation field artificially. A high-resolution H-1 NMR spectrum of ethylbenzene was obtained under the unstable field after compensation with this method. (C) 2007 Elsevier Inc. All rights reserved.