The study on protection devices of MMC based DC distribution network is widely based on digital simulation software such as PSCAD/EMTDC, which brings shortcomings such as the simulation response characteristics without authenticity, inconvenience of developing and extension. In view of that, a hardware-in-loop(HIL) simulation platform which combines RT-LAB with protection devices is built firstly for the typical four terminals MMC Based DC distribution network in Shenzhen. The plantform solves the real time simulation problem of the high frequency DC transformer by the particular eHS technology, enhances the simulation timeliness and proticability with a high degree of confidence. Three typical fault simulaton experiments are tested based on the HIL platform, and the experimental results show that the protection configuration is suitable for the MMC based DC power distribution system, and the action is quickly and accurately. The conclusions can be directly applied to dynamic simulation test and can provide reference for further engineering construction.