Modular multilevel converter (MMC) is considered as the preferred topology for HVDC transmission due to its distinct features. However, the conventional half-bridge sub-modules based MMC (HB-MMC) is endangered under the DC side short-circuit faults. This paper proposes an improved HB-MMC topology with the capability of handling DC side short-circuit faults. For each arm, a standby fault path is constructed and an auxiliary switch sub-module is added. The fault current is fully transferred to the standby fault path by turning off auxiliary switch sub-module when DC short-circuit fault occurs. Then the standby fault path can be deactivated directly to block the fault paths without waiting for the DC side fault current decaying. The proposed IHB-MMC can achieve relatively fast DC fault active clearance with few additional losses. The feasibility and validity of proposed topology are verified by simulation results.