The invention discloses a preparation method of ultrathin modified hydrotalcite and an application thereof to a rubber gas barrier thin film material. Firstly, coprecipitation is used for preparing ultrathin hydrotalcite with a high length diameter ratio, surface modification is carried out, spin coating method technology is used, the ultrathin modified hydrotalcite and rubber are compounded in order to form a film, and finally the gas barrier thin film material is prepared by compounding the ultrathin modified hydrotalcite and the rubber. The ultrathin hydrotalcite with a nanometer sheet shaped structure has high length diameter ratio, and can be used as a filler for substantially prolonging diffusion path of oxygen molecules in a thin film material; surface modification of hydrotalcite can improve interfacial compatibility between hydrotalcite and rubber, and reduce free volume, so that the composite thin film materials has excellent gas barrier performance, good heat stability and mechanical performance. The method has wide source, low cost, and simple preparation, and accords with environmental protection requirements; and the method has wide application prospects in the fields of automobile industry, outdoor packaging and aerospace industry.