As the trend toward compact sizes in electronic products, size reduction has become one of the most important aspects of motor design. In this paper, a miniature axial-flux brushless motor with flexible printed circuit board (FPCB) winding is shown. In order to avoid the mechanical destruction during testing, this paper proposed a characteristic estimating method to measure the performance of the proposed motor. In addition, an implemented motor with drive ICs is established to verify the proposed method. The method is first to drive the motor operating under the two-phase-on mode, and then determine the value of back-EMF constant. While the rotating speed, the motor voltage and winding current are then acquired, most characteristic parameters could be calculated eventually. Contrary to the traditional characteristic testing, this method needs no extra loading and coupling. Having practiced the estimating, a discussion is given to examine the achievement of this study.