Abstract: In order to realize the construction of geospatial data system integrating land and sea, it is necessary to express geographic information in unified datum. Shandong Province carried out the construction of vertical datum conversion model between land and ocean vertical data. This study made use of tide station data, satellite altimetry data and other multi-source data, combining with tidal numerical simulation, harmonic analysis and model optimization and other technical means, to establish tidal models, mean sea surface height models and sea surface topography models, etc. This study constructed 85-height depth datum model with spatial resolution of 1.2'×1.2' and the error of within 15 cm, and consequently realized the conversion between height data and depth data in Shandong coastal area, which provides a method and theoretical basis for the unification and transformation of vertical data in China's sea area and even in the global ocean.