Traditional protection scheme for transmission line usually adopts three-step protection scheme. To promote the property of transmission line protection， this paper presents a new protection scheme for transmission line that is five-step protection scheme. The insensitive zoneⅠis used to improve the operating speed of zoneⅠof transmission line protection. The sensitive zoneⅠis used to improve the sensitivity of zoneⅠ.The insensitive zoneⅡis used to improve the operating speed of zoneⅡof transmission line protection， and it is also used to enhance property to detect arc-resistance fault. The sensitive zoneⅡis used to improve the protection sensitivity of zoneⅡand is used to improve the operating speed of backup protection of the next circuit. ZoneⅢ is used as the backup protection of the transmission line and also used as the backup protection of the next circuit. The paper analyzes the characteristics of the new protection scheme for transmission line. The analysis results show that if the protection relay is made up of microcomputers， the property of transmission line protection can be improved without increasing the hardware of microcomputer protection relay.