Monocellular Raman spectrums of normal liver cell line (LO2) and carcinoma liver cell line (SMMC-7721) were studied with laser tweezers Raman spectrums system and each cell was investigated in three different points,the result of which showed:significant differences of average Raman spectrums were found between the normal cell and the carcinoma one;And,the spectra line of carcinoma cell became weak at the whole;Additionally,the spectral peak intensity ratio of normal cell at 1658cm-1 and 1450cm-1 was 0.63 while that of carcinoma was 0.99;Moreover,the structure and the amount of protein;nucleic acid,lipids and other such molecules had also changed. Average Raman spectrum of monocell was analyzed with the principal component of PCA,the result of which suggested normal cell and carcinoma cell could be differentiated with PCA. All these indicate that judging normal liver cell and carcinoma cell with laser tweezers Ramam spectrums is an efficient method.