Objective To reveal the streaming potential in human dentin and the related influencing factors. M ethod Fresh human third molars without visible evidence of caries were used in this investigation. A cell was designed and manufactured for facilitating the measurement of steaming potential in human dentin under a simulated physiological condition. A system including the cell, a mechanical testing machine, a scanner and a personal computer was established for cyclic loading and data acquisition. The streaming potential of the dentin specimens was evaluated under the loading frequency ranging from 0.05 to 0.2 Hz. Subsequently, a hole of 0.5 mm in diameter was drilled in each dentin specimen for simulating the effect of deep caries on the streaming potential in dentin, the streaming potential of these dentin specimens were reexamined. Results Human dentin revealed streaming potential under testing condition. The value of streaming potential increased with the increase of the frequency of cyclic loading. The phenomenon may result from the increasing difference of pressure between the opposite surfaces of the dentin specimen upon the increase of velocity of the fluid through tubules as a result of increasing loading frequency. Introducing small hole into dentin specimen resulted in the decrease of peak streaming potential. C onclusion Human dentin revealed steaming potential as loaded cyclically in a simulated physiological condition. Increase of loading frequency lead to the increase of streaming potential. Introducing small hole into dentin specimen resulted in the decrease of peak streaming potential.