Combined with theoretical analysis and simulation test， the characteristics of grounding fault at converter transformer valve side of inverter station are analyzed. With the action of the protection related to the grounding fault at converter transformer valve side of inverter station， the valve bypass would be requested and this action strategy would affect the operation of another pole. At last， some improvement suggestions are discussed， which are valuable to complete the action strategy of high voltage DC（HVDC） transmission protection and improve reliability of the HVDC system.