Reusing a pool liner is not recommended. Liners shrink and become brittle when out of the water. If reusing your liner is necessary, take precautions during installation so your pool does not get destroyed in the process.
When Reusing Is the Only Option
Once a pool liner is away from water it will shrink and can become brittle enough to crack. A liner that is less than a year old has a better chance of successful reinstallation. Build your pool on a hot day for the best results by letting the heat warm the liner so it is easier to stretch.
An overlap liner runs up the wall and over the top edge of the pool. You have a better chance of successfully installing a used version of this type of liner. If there is shrinkage, the liner may have less overhang, which is not problematic as long as it reaches over the top of the pool.
A beaded liner runs up the wall of the pool and snaps into a track at the top. Because there is no extra vinyl at the top, any shrinkage will prohibit it from fitting into the track. If it fits but does not stretch during filling, the weight of the water can collapse the pool walls by putting them under too much stress.