Integrated Sensing and Communication (ISAC) technology is vital in the advancement of multifunctional radio applications of the sixth-generation (6G) ecosystem. One of the primary challenges in ISAC systems lies in understanding and interpreting wireless channels for both sensing and communication purposes. A clear relationship between these channels would allow ISAC systems to reduce the complexity of channel estimation. This paper introduces a framework for reconstructing communication channels using monostatic sensing channels within an ISAC system. We first geometrically illustrate the synergies and differences between the sensing and communication regions determined by frequency intervals. Subsequently, we construct a communication propagation channel based on overlap determined by this geometric relationship and a simplified monostatic-to-bistatic equivalence theorem. Lastly, we combine multipath located in the same delay bin to construct channel state information (CSI), taking into account the bandwidth constraint. Channel measurements and ray-tracing simulations demonstrate that the proposed framework accurately generates communication channels. Finally, the numerical results reveal the impacts of environmental and system constraints on key characteristics of the channels.