When electrospinning has been used as a special technology of regenerative bone scaffold, for raising the efficiency of electrospinning and decreasing collecting area, the mechanism of bending instability was analyzed and concluded that the force of electric field is a key factor. Auxiliary gradient rings have been added to electric field, which changed the environment of electric filed. Then, it was verified that additive gradient rings could reduce the collecting area. On the other hand, Maxwell was used to analyze the strength and structure of electric field. The maximum intensity of electric field existed in the position of nozzle. The farther apart from nozzle, the rapidly intensity decreased. When auxiliary gradient rings had been added, the intensity of instability stage showed increased trend. Mechanism analysis and experimental result were confirmed by the simulation effectively.