Abstract: A method for modeling structural planes of rock mass was proposed by combining definite structural planes with random ones. Definite structural planes were obtained according to the data from engineering geological exploratory survey, while random ones were generated by 3D network simulation technique using the data from digital photogrammetry. A mechanism was introduced to dynamically check/adjust the random structural planes based on the real-time data acquired from the construction in progress, thus a more accurate model was established. Based on the model, unstable blocks can be found out using the GeoSMA-3D system developed by the authors, which has great significance for rock mass stability forecast and dynamic design/construction.