In order to fully exert the advantages of LCC and MMC and enable the MMC to have DC fault ride through capability, this paper researches a new LCC-MMC hybrid HVDC system. The system uses traditional LCC in the rectifier side and cell-hybrid MMC in the inverter side. The MMC consists of half-bridge sub-module, full-bridge sub-module and clamp-double sub-module, and has the function of over modulation working and DC fault pass through. It emphatically analyzes the start-up process of the hybrid HVDC system, and then offers the start-up control strategies of the LCC and VSC. Finally, the experimental verification on the built 24 kW hybrid HVDC system indicates that this start-up strategies is feasible and available. This work is supported by National key Research and Development Program of China “key technology research and demonstration of high-voltage large-copality flexiblex DC grid”.