Abstract: A gene chip includes a chip carrier, a plurality of DNA nanoballs assembled on the chip carrier, and a polymer film formed on the chip carrier and wrapping the DNA nanoballs. The polymer film includes at least one of a film of a positively charged polymer, a film of a positively charged polymer which is modified, a film of a zwitterionic polymer, and a composite polymer film. The composite polymer film is formed by a layer-by-layer self-assembly process of a positively charged polymer and a negatively charged polymer. The gene chip has good sequencing quality and different functions can be achieved by coating with different polymers, such as the chip surface rapidly drying out and surface non-specific adsorption. A method of preparing a gene chip is further disclosed.