Based on more than 100 references, the present paper reviews the progress in the application of nuclear magnetic resonance (NMR) spectroscopy, an effective method to study the variation in chemical composition and molecular structure in biological samples for early diagnosis of cancer at molecular level. In the past several decades, numerous works have demonstrated that NMR spectroscopy may be developed into a sensitive diagnosis method to detect cancer in early stage. Because of the rapid development of NMR spectroscopic techniques, it becomes possible to record NMR spectra of biological samples in both in-vitro and in-vivo manner. Systematic spectral differences between biological samples from cancer patients and normal controls can be observed from both liquid-state and solid-state 1H, 31P NMR spectra and used to reflect the changes in metabolic behavior of malignant tissues. This paper has summarized NMR spectroscopic investigation on biological fluid, cultured cancerous cells, resected tissues, as well as in-vivo malignant tissues by using various advanced NMR techniques including recently developedhigh-resolution magic angle spinning (HR-MAS)and magnetic resonance spectroscopy and imaging (MRSI) methods. First, characteristic peaks, which are related to choline, phosphocholine (PC) and glycerophosphocholine, can be observed in both 1H and 31P NMR spectra of biological fluid samples from cancer patients. These results indicate that alternation in the metabolic pattern occurs with the progression of cancer. The research on cultured cells by using NMR spectroscopy showed that the signal of various phospholipids and their metabolites such as PME increased significantly in cultured cancer cells. For resected tissues, two methods can be utilized. The first one is to investigate the tissues directly by using HR-MAS spectroscopy. The second method is to extract various metabolites with various solvents such as CHCl3/methonal mixtures, HClO4 solutions, etc. and then analysis of the extracted solutions is performed using conventional liquid NMR spectroscopy. Significant differences on the content of various amino acids, metabolites of phospholipids, can be observed between malignant tissues and normal controls in NMR spectra. Recently, MRSI that can acquire 1H-NMR spectra of suspected tissues during the process of MRI diagnosis is available. The approach makes it possible for the surgeons to judge whether the suspected tissues are malignant or not before surgical operation. The above results demonstrate that NMR spectroscopy possesses bright perspective in diagnosing cancers and differentiating different types of cancers based on the metabolic behavior of cancerous tissues.