A method for systematically investigating the DNA space structure of different issue during the occurring process of adenocarcinoma is proposed, by incorporating issue DNA extraction technology and Raman spectroscopy technology. In experiment, DNA solutions of normal gastric mucosa, intestinal metaplasia and adenocarcinoma are firstly extracted, and then their Raman spectra are measured, respectively. According to the Raman spectra, genomic DNA is analyzed in detail. The experimental results show that: DNA of normal gastric mucosa has stable phosphate backbone; Since the peak intensity at 1 090 cm-1 is lower than that at 1 050 cm-1, phosphate backbone in DNA of intestinal metaplasia becomes unstable, while the rest spectra peaks are similar to those in normal gastric mucosa; In terms of adenocarcinoma DNA, double peaks at 1 090 cm-1 whose intensity are higher than 1 050 cm-1, are observed, which indicates that DNA chain is broken and re-forms a double stabilized phosphate backbones. In addition, peaks at 950 cm-1, 1 010 cm-1, 1 100~1 600 cm-1 also exhibit obvious difference compared with normal gastric mucosa, which shows that deoxyribose and bases are changed due to broken of DNA. All these results indicate that the DNA variation process during the occurring process of adenocarcinoma may be: the stable DNA phosphate backbone in normal gastric mucosa change into unstable DNA phosphate backbone in intestinal metaplasia issue under affecting of pathogenic factors, and finally, DNA phosphate backbone is broken and re-forms a double stabilized phosphate backbones, which causes the occurring of adenocarcinoma.