A fabricating method of a flexible substrate is provided, including: step 1: fabricating a first flexible base; step 2: fabricating at least one layer of a laminated material made of silicon oxide and amorphous silicon on the first flexible base; step 3: performing a dehydrogenation treatment to the laminated material; and step 4: fabricating a second flexible base on the laminated material to obtain a flexible substrate. Compared with the prior art, by disposing two layers of flexible bases and a laminated material between the flexible bases, the stability of multiple bending can be improved; by performing a dehydrogenation treatment of the laminated material, the defects of the flexible substrate in the back-end process can be reduced.