The invention discloses a plug protecting sheath which closely sleeves outside a standard plug. The plug comprises a plugging part which is used for inserting into a socket and a handheld part of which the cross section shape is rectangular. The sheath comprises a substrate. The top surface of the substrate has a boss. A stepped hole penetrates through the boss and the substrate. The hole wall ofthe stepped hole is in tight fit with the plug, thereby realizing plug sealing. The plug protecting sheath cooperates with the standard plug and is developed through performing appropriate improvementon the profile dimension parameter of the plug. The plug protecting sheath truly prevents water inflow into a power interface through multiple sealing facilities, thereby preventing accidents of water leakage, electric leakage and shortcircuit. Furthermore an effect of protecting body safety of a consumer is realized.