Metal-oxide surge arrester for DC systems is used in DC power system to protect DC electrical equipment from being damaged by over-voltage. The arrester is designed and produced according to Metal-oxide Surge Arresters without Gaps for DC Systems of 3kV and below (NB/T 42049-2015) and Railway Applications - Fixed Installations - DC Switchgear - Part 5: Surge Arresters and Low-voltage Limiters for Specific Use in DC System (GB/T 25890.5-2010, EQV IEC61992-5) which were prepared with the participation of Xi'an Shendian. It was developed according to the Technical Report (Cigre 33/14.05) of International Conference on Large High Voltage Electric System and Guidelines of Metal Oxide Surge Arresters without Gaps for HVDC Converter Stations (GB/T 22389-2008), in combination with the production status of DC arresters at home and abroad and the multi-year experience of Xi'an Shendian in the arrester design and production. The arrester has reasonable structure and reliable performance. The resistor is DC metal oxide resistor that is independently developed by Xi'an Shendian, with such advantages as low residual voltage, high impulse current withstand level, high energy absorption capacity, and low operating power consumption under DC voltage. The polymer housing is formed by one step with integral moulding and curing process, to provide high sealing performance and long service life to the arrester. The arrester can be configured with disconnector. When the arrester is damaged, the disconnector will make the arrester out of operation and give a clear sign to prevent against ground fault and make the system safer. According to demand, the arrester can also be configured with no residual voltage counter which will not increase the residual voltage of the arrester, making the device safer. LCD display of the counter provides intuitive and clear reading. With built-in power supply, high integration, small size and fully sealed structure, the counter is suitable for indoor or outdoor applications. The arrester has passed the comprehensive type tests (including 40kA short-circuit current test) of the National Quality Supervision and Inspection Center of Insulators & Surge Arresters. The product has been used in the rail transit systems of major cities such as Beijing, Shanghai, Guangzhou, Shenzhen, Chongqing, Nanjing, Chengdu, Hangzhou, Harbin, Changchun, Shenyang, Hong Kong and Xi'an, as well as the urban mass transit systems of Ethiopia and other countries. With excellent protection performance, the product is reliable.