The invention discloses a self-adaptive resonant frequency method and a self-adaptive resonant frequency device. The self-adaptive resonant frequency method comprises the following steps: when a terminal receives a card search request from an upper computer, the terminal executes the following steps: step 1, the terminal carries out card search according to a yield value and obtains a card search result; step 2, the terminal judges whether card search is successful according to the card search result, if so, the terminal returns an operation result to the upper computer, if not, the terminal executes step 3; step 3, the terminal updates an error code according to the card search result; step 4, the terminal adjusts the yield value according to the error code; and step 5, the terminal judges whether the adjusted yield value is in a first default range, if so, the terminal executes the step 1, and if not, the terminal returns card search failure information to the upper computer to finish. By utilizing the self-adaptive resonant frequency method, the yield value of the smart card signal received by the terminal is automatically adjusted according to error type generated in card search process, and the communication efficiency of the terminal and a smart card is improved.