A new subjective wave-front aberrometer, which measures ocular wave-front aberrations, is studied. The working principle and design project are presented. The method of three optical channels is used to design the optical system. The key technologies of multi-threading, video collecting, image processing and the control of single-chip microcontroller and stepping motors are used to realize three-dimensional real time automatic tracking of pupil. All the seven order ocular aberrations are measured with the aberrometer. The ocular aberrations are described with Zernike polynomials, two-dimensional and three-dimensional wave-front aberration maps. The formula of every order wave-front aberrations' RMS is obtained. 110 eyes of 57 patients were measured three times for clinic investigation. The difference between the gradually descending values of every wave-front aberrations' RMS was not significant (P >0.05) with SPSS software. The results show that the repeatability and accuracy of the aberrometer are good.