Water flooding by horizontal wells is widely applied in porous carbonate oilfields at Middle East. However, the rapid increase in water cut is a big challenge to efficient oilfield development. And accurately description of the dominant waterflooding channels is crucial to overcome this issue. Due to the small proportion and subtle characteristics of high permeability channels in carbonate reservoirs, conventional modeling struggles to accurately depict these channels, leading to an unclear understanding of water breakthrough paths between horizontal wells. This paper presents a fine description method for reservoir heterogeneity characteristics and dominant waterflood channels. Firstly, based on the interpretation results of logging data from horizontal wells, a geological model is established that reflects the distribution of physical properties along the horizontal section. Secondly, an amplification formula is applied to magnify the permeability index of relatively high permeability intervals. Subsequently, a dynamic model is established based on the magnify permeability, that accounts for temporal changes, and complete the historical matching by adjusting the permeability magnify parameters. Finally, the well-fitted model is conducted to dynamically characterize the waterflood channels in horizontal wells. The results demonstrate that for different types of water-producing injection and production well groups, good history matching can be achieved by the reservoir dynamic models established with different permeability amplification parameters. For wells with slow water breakthrough, fast water breakthrough, and sudden water breakthrough, the permeability amplification multiples for the high permeability intervals are 1 ~ 2, 3 ~ 7, and 8 ~ 15, respectively. These models can accurately depict the formation process of water breakthrough channels during the water flooding, as well as their spatial distribution and distribution along the horizontal wellbore. The result provides guidance for rational production-injection allocation and implementation of water management measures in horizontal wells.