In the present paper, NMR spectroscopy, an effective tool to detect the variation in molecular structure and changes in chemical composition of metabolites in tissues, was used to study the differences between malignant and normal tissues from rectum. 1H spectra of four malignant rectum tissue samples and two normal control tissues were investigated by using a 500M NMR high-resolution magic angle spinning magnetic resonance spectrometers (HR-MAS NMR). The results indicate that the 1H HR-MAS spectra of rectum cancer tissues are significantly different from those of the normal controls and most differences are presents in the form of variation in the relative intensities of the characteristic peak of various metabolites. In order to characterize the variation in the relative intensities in a quantitative manner, the intensity of the methyl peak of fatty acid at 0.88 was utilized as inner standard. Systematic differences between NMR spectra of malignant tissue and normal controls are as follows: (1) The concentration of amino acid increases significantly in malignant tissues, since the relative intensities of characteristic peaks of amino acid including valine, isoleucine, leucine, lysine, glutamate, glutamine, and aspartate are stronger in the NMR spectra of the malignant tissues. This phenomenon may reflect the fact that the activity of protein synthesis is enhanced in cancerous tissues. (2) The intensities of the characteristic peaks of lactic acid in malignant tissues are higher than those from normal controls. This may be related to the nature of anaerobic metabolism activity in malignant tissues. (3) The level of choline and its derivatives, taurine and creatine, increases significantly in malignant tissues, suggesting that the metabolic activity of malignant tissues changes. (4) In the spectral region between 4.5 and 10, observable changes occur on the peaks for unsaturated fatty acid and nuclear acids. Therefore, the above spectral variations in high resolution magic angle spinning NMR spectroscopy may be utilized as a potential tool to diagnose rectum cancer.