In order to maintain the constant temperature of the constant temperature region of the directly tuned electrical/optical conversion module laser, a new type of thermal isolation high-frequency signal transmission structure is proposed. This structure uses a capacitor of a low thermal conductivity medium to transmit high-frequency signals, increasing the heat transfer resistance between the radio frequency and the laser chip in the electrical/optical conversion module effectively, and reducing the heat conduction from the radio frequency to the constant temperature region of the laser chip. The simulation results show that compared with traditional circuit chip overlap structure and gold wire cascade structure, the proposed transmission structure reduces the thermal load of the semiconductor cooler by 20.5% and 10% respectively, and reduces the current by 100 mAand 60 mA respectively. At the same time, the maximum return loss of this transmission structure in the frequency range of 2~18 GHz is only -16.7 dB, which has good radio frequency transmission performance.