Transient voltage suppressor (TVS) is an interface protection device in the form of a diode, in which a low-voltage TVS is usually composed of a low-resistance epitaxy and a high-concentration doped region on its surface. During the chip manufacturing process, the surface doping concentration of the wafer has a great influence on the device characteristics, and abnormal impurity diffusion changes can easily lead to abnormal device parameters. This paper investigates and confirms the abnormal parameters in the manufacturing process of a low-voltage TVS. It is confirmed that the abnormality is caused by the high surface doping concentration, and the trends of the surface doping concentration and device parameters are analyzed and verified by experiments.