A double variable sliding isolator including a bottom sliding plate, a top sliding plate, and a friction piece is provided. The bottom sliding plate has a bottom sliding surface that has at least two curvatures. The top sliding plate is disposed over the bottom sliding plate and has a top sliding surface that has at least two curvatures. The friction piece is disposed between the top sliding plate and the bottom sliding plate and the friction piece is in contact with the bottom sliding surface and the top sliding surface. When an external force is applied to the bottom sliding plate and the top sliding plate, the bottom sliding plate and the top sliding plate will generate a relative displacement, so that the friction piece slides along the bottom sliding plate and the top sliding plate.