Nonlinear optical spectroscopy has wide applications in the medical field with special advantages. Through combining nonlinear optical spectroscopy with membrane electrophoresis, we endeavored to develop a novel method for blood serum analysis for cancer detection applications. In this method, albumin and globin are isolated from blood serum by membrane electrophoresis to perform two-photon excitation fluorescences (TPEF) spectral analysis. The obtained spectra present rich signatures of the biochemical constituents of whole proteins. We evaluated the utility of this method by analyzing albumin and globin samples of blood serum from esophageal cancer patients and healthy volunteers. Twophoton excitation fluorescences revealed that esophageal cancer group can be unambiguously discriminated from the normal group, and I457/I639, I511/I639, and I543/I639 ratios can be used as indicators to diagnose early esophageal cancer. These results are very promising for developing a label-free, non-invasive clinical tool for early cancer detection and screening.