The invention discloses an information transmission realization method and a system, main control equipment and an intelligent card. The method comprises the following steps that: the intelligent card notifies the supported work modes to the main control equipment; the intelligent card receives a clock frequency returned by the main control equipment, the returned clock frequency is determined by the main control equipment according to the notified work mode, and the clock frequency returned by the main control equipment is a second clock frequency under the condition that the main control equipment determines that the intelligent card supports the externally provided clock frequency according to the work modes notified by the intelligent card; the intelligent card judges whether the intelligent card per se can support the second clock frequency returned by the main control equipment or not; and the intelligent card and the main control equipment carry out information transmission on the basis of the clock control signal with the frequency of second clock frequency under the condition that the judgment result shows that the intelligent card per se can support the second clock frequency returned by the main control equipment, or the intelligent card is based on the clock control signals with the frequency of the first clock frequency and the main control equipment is based on the clock control signals with the frequency of the second clock frequency for carrying out information transmission.