In order to simulate the operating characteristics of actual DC system accurately, a full-digital simulation modeling method is proposed based on HCM3000 control and protection platform. Firstly, simulation modeling scheme is introduced, which explains the modeling process of project platform. Secondly, the function realized by hardware device is simulated digitally. Communication interface of the graphical software program is modified and then converted into simulation executable program. Through the task calling program, the order calling of control and protection codes is realized. Finally, taking Zhalute-Qingzhou UHVDC transmission project as an example, DC system simulation model is established. A large number of function performance tests and comparison with actual project waveforms are completed. Results show that simulation model is highly consistent with actual project operating characteristics, which verifies the accuracy and effectiveness of full-digital simulation model. It can reproduce operating characteristics of DC system, which has important guiding value for actual project operation and maintenance. This work is supported by Science and Technology Project of State Grid Corporation of China (No. SGTYHT/17- JS-199) “Key Technology Research and Application of Field Test and Operation & Maintenance Optimization of UHVDC Control and Protection System”.