Future wide-swath altimetry missions will provide high-resolution information about ocean surface elevation, and facilitate the characterization of meso- and sub-mesoscale ocean activities. In this study, the demand analysis of three-dimensional (3D) oceanic state reconstruction on wide-swath SSH data features was evaluated using a data assimilation strategy. Three groups of experiments were performed to determine if the wide-swath altimetry observations would improve the three-dimensional (3D) field estimates of ocean temperature-salinity-velocity (T-S-V), and to evaluate how the spatial and temporal resolution and accuracy of the wide-swath altimetry observations affected the ocean state estimation. The Regional Ocean Modeling System and the four-dimensional variational data assimilation method were used in the experiments, with numerical simulation for the Taiwan region at a resolution of 1/10° as the example. The sensitivity of the 3D ocean state construction to the wide-swath altimetry measurements was also investigated. The results showed that the wide-swath sea surface height (SSH) measurements would have an overall positive impact on the 3D T-S-V field and that the positive effect would increase as the resolution and accuracy of the observations increased, but the net benefits would gradually decrease. Among the three examined features of the wide-swath altimetry observations, the temporal resolution had the most influence on the 3D ocean state analysis.