Proton of water, as a probe, can be used to explore changes of moisture content in wood through nuclear magnetic resonance (NMR). NMR provides a new way for the quantitative determination of wood moisture content (MC). The changes of water in walnut, red oak and ash in desorption process were analyzed through free induction decay (FID) curve of nuclear magnetic resonance. The results showed that the relationship between wood sample MC and FID signal amplitude was highly linear, with R2 above 0.99. Therefore，wood moisture content can be measured with NMR by establishing a standard curve of wood MC and FID signal amplitude. Also the basic density of different wood species can be compared through FID signal intensity of dried wood.