A co-detection method based on gold nanoparticles and microarrays is reported for detecting multiple biomarkers. A gold nanoparticle/antibody composite is synthesized as detecting probe. The gold deposition staining with HAuCl4 and H2O2 produces a color change that can be observed with the naked eye. This protein biochip is capable of detecting multiple biomarkers in 12 serum samples simultaneously in 1 h. The results confirm the clinical significance of DKK1 as a serologic marker of lung cancer.