A thin-film transistor structure having a three-dimensional (3D) fin-shaped channel and a manufacturing method thereof. The manufacturing method comprises the following steps: (a) depositing a bottom gate (2) on a substrate (1) and etching the same; (b) depositing a bottom dielectric layer (3) at an upper portion of a structure obtained from Step (a), and consecutively depositing semiconductor thin film layers on the bottom dielectric layer (3); (c) etching the semiconductor thin film layers to obtain a fin-shaped channel (4); (d) respectively depositing an ohmic contact layer (9), a source (5), and a drain (6) on two sides of the semiconductor thin film layers and etching the same; (e) depositing a top dielectric layer (7) and top gate (8) on an upper portion of a structure obtained from Step (d); and (f) etching the top gate (8), thereby completing manufacturing of a thin-film transistor having the two gates and the 3D fin-shaped channel. The resultant transistor has an increased thickness of a channel region semiconductor thin-film, and reduces a thickness of a source or drain region semiconductor thin-film, thereby realizing a preferred light absorption and switching property.