In order to eliminate the subdividing error caused by fring signals which is not in phase quadrature, a new method that can directly subdivide fringe signals for random phase relationship is presented. One signal period can be divided into eight sections according to the fringe signals polarity and amplitude. The fringe signals are sampled at high speed so that the section in which the sampled point locates can be calculated in real time. The fringe signals absolute amplitude joints can be dynamically traced by judging whether two successive sampling points are in different sections. After the amplitudes of fringe signals star point and stop point are sampled, the section in which they locate can be calculated, the fraction fringe can be worked out by combination of joints of start point and stop point. Experimental results show that the new method can subdivide fringe signals correctly even when they are in random phase relationship. This new method breaks through the limitation that the signals must be in phase quadrature for conventional subdividing methods and has better anti-jamming ability.