Aiming at the barrier coverage problem of wireless sensor networks（WSNs）in mountainous areas in three dimensional（3 D）space

an algorithm of ring-barrierconstruction based on contour area is proposed.The simulation results show that the more WSNs nodes deployed in the network

the more nodes constitute ring-barrier

but the total length of the barrier becomes shorter.On the contrary

the number of nodes forming the ring-barrier is small

but the actual length is longer.This algorithm can form ring-barrier in the contour area of mountains

but when the density of deployed WSNs nodes is low

it cannot build barriers across the contour area

which will be the next research work.