Three-dimensional geologic modeling for quantitative characterization and realistic visualization in the Pohang Basin, Korea is performed by using GOCAD (geological object computer aided design) software. The study area is located in entire Haedo-Dong, Nam-Gu, Pohang-Si, Gyeongsangbuk-Do, Korea and is long in the east-west direction 1,200 m, the south-north direction 2,200 m, and 2,176 m depth. Geographic information systems (GIS) and borehole (A, B, C, DS-1, DS-2, PY-2, 301, and 302) data are collected and analyzed first. As a result, the study area is composed of the cretaceous igneous rocks, tertiary continental sediments, and marine sediments. The cretaceous igneous rocks are classified into the plutonic rocks and volcanic rocks, and the tertiary marine sediments are classified into the Hakrim, Heunghae, Idong, and Duho Formation. Meanwhile, there is no fault structure in this study area. First, through the primary analysis of raw data, three-dimensional structural modeling is performed by using discrete smooth interpolation (DSI) algorithm. Then, three-dimensional grid model composed of total 2,046,000 deformable cells is then constructed and three-dimensional geologic formation modeling is performed by integrating three-dimensional structural model and three-dimensional grid model. In addition, in order to estimate and analyze the distribution of lithofacies in uninvestigated area, variogram modeling and three-dimensional lithofacies modeling is performedin 100 times by using sequential indicator simulation (SIS) and truncated Gaussian simulation (TGS). In this case, since the cretaceous plutonic rocks, volcanic rocks, and tertiary continental sediments compose of granite, tuff and conglomerate as single lithofacies, respectively, three-dimensional lithofacies modeling is performed only of the tertiary marine sediments including Hakrim, Heunghae, Duho, and Idong Formation. Three-dimensional lithofacies modeling simulation results show that the mudstone is distributed remarkably much more in comparison to the sandstone in the tertiary marine sediments. In addition, according to result of statistics analysis, the result of TGS shows that sandstone is distributed in relatively smaller ratio compared with the result from SIS. In addition, the ratio of mudstone and sandstone used in SIS is similar to raw data than TGS. To assess the quality of the results of three-dimensional lithofacies modeling, Cross-validation is performed. As a results of cross-validation, it is confirmed that the deep borehole PY-2 among the six boreholes indicate the highest level of dependence for three-dimensional lithofacies modeling.