The invention discloses an experimental method for improving condensate gas reservoir recovery efficiency by CO2 injection. The method comprises the following steps that a condensate gas reservoir fluid PVT physical property parameter is tested; and based on the obtained condensate gas reservoir fluid PVT physical property parameter, a constant volume depletion experiment is used as a test basis, and an isovolumetric air-entrapping experiment is conducted. According to the experimental method for improving the condensate gas reservoir recovery efficiency by CO2 injection, a reasonable working system can be optimized, the difficulties that currently, condensate oil and gas reservoirs are exploited in a depletion method, energy falls fast, condensate oil is lost underground, and the recovery degree is low are solved, and a foundation is laid for compiling a condensate gas reservoir CO2 injection development program and effectively improving the condensate oil and gas reservoir recovery efficiency.