A fiber containing nanobubbles and a fabrication method thereof are provided. The method includes providing a polymer material to mix with a photoactive compound to form a mixture. A spinning process is performed to the mixture to form fibers. After the fibers are solidified, a light irradiation or a thermal treatment is performed on the solid fibers to make the photoactive compound releases a gas. The gas forms a plurality of closed nanobubbles in the fibers and the nanobubbles have a size between 300nm and 800nm.