Vines can be extremely difficult to control. They tend to grow fast and quite aggressively, growing into garden beds, up trees and across lawns, to name a few. If your vine has thorns and you are having troubling killing it, it may be the common weedy vine known as smilax or greenbrier. Whatever type of thorny vine you have, if possible, it's best to kill it while its young before it gets out of control and before its root system becomes large and harder to kill.
Wear thick garden gloves when working with vines with thorns. Also, wear long, old clothing that you don't mind getting ripped by the thorns.
Cut down the thorny vine using pruning or lopping shears. If the base of the vine is too thick for loppers, a saw may be necessary. If the vine has thin stems, a weed trimmer may work.
Dig into the soil to examine the vine's roots. If they are tubers or rhizomes, which grow close to the surface and are easy to remove, dig as many of them as possible out of the soil and discard. This will help minimize new growth.
Paint any stumps left behind with an herbicide labeled as a brush killer, or if you know the identity of your bush, select one labeled to kill it.
Spray the leaves on new growth with a brush, broad-leaf or non-selective herbicide, per label instructions. Again, if you know the identity of the vine, choose an herbicide that lists it on its label. If you are using the herbicide in an area where it can also kill nearby plants or grass, paint the herbicide on the vine's leaves rather than spraying it.
Reapply the herbicide whenever the thorny vine grows. It may take one to two years of persistence to kill the vine completely.