Investigations on near infrared surface-enhanced Raman scattering (NIR-SERS) spectra of the serum for patients with liver cancer and healthy persons based on Ag nanofilms prepared by using electrostatic self-assembly are reported. Analysis indicates NIR-SERS spectra of the sera between healthy persons and liver cancer patients are different. Firstly, Raman bands at 630, 720, 812 and 1578 cm-1 become weaker (even disappear) in NIR-SERS spectra of the sera for cancer liver patients but stronger in NIR-SERS spectra of the sera for healthy persons. Secondly, Raman bands at 1130 cm-1 and 1204 cm-1 in NIR-SERS spectra of the sera for healthy persons have blue shifts to 1135 cm-1 and 1269 cm-1 in NIR-SERS spectra of sera for cancer liver patients, respectively. Meanwhile, a new Raman band at 558 cm-1 appears in NIR-SERS spectra of liver cancer patients. Additionally, striking spectral differences are abvious in NIR-SERS spectra in the intensity ratios at 630/300, 1130/300, and 1578/300 cm-1. These three peak-intensity ratios of liver cancer patients with values of 0.848±0.042, 1.094±0.118, 0.914±0.070, respectively, are more notable (mean±S.D., n=15, P<0.01) compared with those of healthy persons (1.985±0.487, 1.568±0.286, 1.189±0.108, respectively). The results show that the intensity relative peak-ratios at 630/300, 1130/300, and 1578/300 cm-1 can be used to discriminate liver cancer patients from healthy persons, which indicate these three intensity ratios can be served as NIR-SERS spectral criteria for the diagnosis of cancer liver.