In order to solve the problem of irreversible damage to the high-speed signal source caused by the conduction/cutoff of the direct current(DC) source or hot swapping of the link during the testing process of traditional T-type biases(Bias-T) in silicon-based high-speed modulators. Firstly, the causes of the problem and the advantages and disadvantages of conventional solutions are analyzed, and then an active Bias-T circuit for silicon based high speed modulator testing is designed. This circuit utilizes the characteristics of transistors in microwave amplifier chips on the basis of traditional Bias-T to isolate the impulse voltage generated by the DC source during feed on/off or hot swapping. Finally, simulation design and testing are conducted on the active Bias-T circuit. The test results show that the bandwidth of the circuit is greater than 25 GHz and the pulse voltage is about ±0.055 V, which eliminates the risk of damage to the signal source equipment.