Infrared (IR) and visible sensors are commonly used in the target tracking and recognition system. Image fusion for these two modal images can effectively improve the system's tracking and detection accuracy. The model of dynamic contour is combined with image fusion and feature points in feature search are used to implement image registration accurately. Meanwhile a new feature-level image fusion is applied. Control points of B-spline curves for the target's contour in two modal images are used to implement a real-time differential coupling. This coupling makes improvement on the differential coupling proposed by Curwen, where a rigid template is transformed into a real-time transformation template with image registration. Moreover, a new dynamic equation is derved for dynamic contour after this image fusion. In this fusion, the dynamic contour's convergent shape in visible image is restricted by the target's contour in IR image. This fusion improves dynamic contour's tracking accuracy effectively. A contrasting experiment on moving hand image sequence indicates average tracking error of dynamic contour has decreased by 60.25% in visible image with this image fusion.