Abstract: In Voltage-Source Converter High-Voltage Direct Current (VSC-HVDC) transmission systems, the Merging Unit (MU) serves as a critical component of the protection system . The accuracy and timeliness of its data transmission directly impact the reliability of protection control. Addressing the accuracy limitations of traditional electronic instrument transformers in fault detection and analog signal transmission, this paper proposes an analog channel data distribution method suitable for hardware-in-the-loop simulation environments. Based on the IEC 60044-8 protocol , this method transmits analog signals required for protection and control via separate optical fibers, achieving redundant data distribution and efficient transmission. This enhances the reliability and response speed of valve-controlled flexible DC systems while reducing the failure rate of DC protection systems.