A pixel structure of an image sensor is provided and includes following units. A crystalline layer of a first doping type is formed on a substrate. A photodiode region is formed in the crystalline layer. A gate of a source follower transistor is formed on a top surface of the crystalline layer. A reset gate is formed on the top surface of the crystalline layer. A doped region of a second doping type is formed in the crystalline layer and formed between the reset gate and the gate of the source follower. The first doping type is different from the second doping type, and the photodiode region is connected to the doped region under the top surface of the crystalline layer as an anti-blooming path.