A 128 × 128 elements liquid crystal (LC) microlens array, instead of the conventional microlens array with a fixed focal length, is proposed to achieve an electrically controlled adaptive tunable Shack-Hartmann wavefront sensor. The sensor can overcome the shortcomings of the traditional wavefront sensor, which can not take both measurement range and measurement accuracy into account, and it can work either in a large measuring range/short focal length, or high measurement accuracy/long focal length modes. It is also free to switch between the two modes. Through experimental measurements, when the operation mode of the wavefront sensor is on the short focal length, it has tunable focal length range of 86~400 μm. While the operating mode is on the focal length, its modulation transfer function is more than 0.46. The extreme experiment is used to verify its feasibility, which is about the focus falling outside the effective region of the CCD. The studies show that the wavefront sensor has a certain electronically controlled adaptive tunable ability. The potential application perspective of this design in an adaptive optics system is also presented.