Abstract: A method for cyclic biochemical conversion of carbon dioxide and hot gas cogeneration in depleted oil and gas reservoirs includes: S1: selecting a target depleted oil and gas reservoir; S2: adjusting a temperature of the target depleted oil and gas reservoir to 30° C. to 70° C. and detecting whether formation water of the target depleted oil and gas reservoir contains methanogenic archaea, in which if no methanogenic archaeon is contained, then methanogenic archaea is injected and step S3 is proceeded, and if methanogenic archaea are contained, then step S3 is proceeded directly; S3: injecting a mixture of carbon dioxide and hydrogen into the target depleted oil and gas reservoir through a gas injection well; and S4: shutting down the gas injection well to wait for the methanogenic archaea to convert carbon dioxide and hydrogen into methane and exploiting the methane and heat energy in the target depleted oil and gas reservoir.