Abstract: There are various types of oil and gas reservoirs in the western part of South China Sea. From the point of view of structural modeling, there are numerous complex fault block oil and gas reservoirs and multi-truncated faults developed in Beibuwan Basin. From the point of view of facies modeling, channel and delta facies reservoirs, with the characteristics of rapidly lateral changing in lithology and anisotropy, are developed widely in Weixinan Depression. In addition, calcareous interlayers are widely spread in the marine facies of Wenchang Oilfields. Based on the study of reservoir geological modeling in recent years, a series of geological modeling methods focusing on the complex reservoirs are summarized. The problem of poor grid quality occurred in the complex structure modeling has been improved by adopting different means such as grid quality control, fault image processing based on stair thinning. The study and application of connectivity probability and uncertainty analysis contributed the significant improvement in the accuracy of facies modeling. A series of effective methods mentioned in this paper have improved the quality and the accuracy of reservoir geological model, and met the requirements of development and production forecast.