It is most critical to acquire exact trace curves in time for realizing the zoom tracking in zoom imaging systems. Therefore,a novel computation strategy for zoom tracking curves is proposed. First,a real-time in-focus point is computed by using an image sharpness evaluation operator based on RAW format. Then, the position relations between zoom motor and focus motor are fitted to acquire the two trace curves at the near end and far end of object distances, which are regarded as the upper and lower bounds of trace curves. Finally, both geometric and adaptive zoom tracking methods are combined to be a hybrid algorithm to acquire the curves at some object distances by the method of interpolation. The trace curves for upper and lower bounds are obtained by a gradient operator on a self-developed zoom imaging system, zoom tracking is implemented with acquired trace curves and the image during zoom tracing is acquired. The obtained results show that the image quality of imaging system using proposed approach is improved by 30% as compared with that of the traditional system.It demonstrates that zoom tracking curves can be applied in focusing, and the image quality is improved dur-ing zoom tracing.