The paper presents a back-up protection scheme for loop system from all types of fault based on the directional element. The traditional back-up protection schemes such as distance protection and overcurrent protection are not suitable for the loop system. This paper shows a novel back-up protection scheme using the wireless communication, when the main protection doesn't work, the scheme provides a precise back-up protection which makes the affected area relatively small. The negative sequence and positive sequence directional elements are used to determine the direction of fault current. The scheme is simulated by the Simulink software and validated by using commercial relays.