The present invention discloses a transistor structure for electrostatic discharge protection. The structure includes a substrate, a doped well, a first doped region, a second doped region and a third doped region. The doped well is disposed in the substrate and has a first conductive type. The first doped region is disposed in the substrate, encompassed by the doped well and has the first conductive type. The second doped region is disposed in the substrate, encompassed by the doped well and has a second conductive type. The third doped region is disposed in the substrate, encompassed by the doped well and has the second conductive type. A gap is disposed between the first doped region and the second doped region.