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The ground-based GNSS has become a member of global meteorological composite observing system with superiority on the derivation of the atmosphere water vapor compared to traditional observation methods. Grid models decide the spatial distribution of the slant path penetrating the grids and greatly affect the tomography results which is key for further operational water vapor tomography to select optimal grid model in ground-based GNSS. The paper gives the effect of three different grid models on the convergence properties and tomography result in the multiplicative technique to reconstruct the 4D wet refractivity field of troposphere based on simulation method for Shenzhen-Hongkong(SH) GNSS network with data from 15th to 22th August,2009. The results show that for SH tomography region, the fundamental irregular grid model induces the worst tomography result, for the extended grid model and fundamental regular grid model which one is better depends on the distribution of satellites related to the ground network during the specular time, if there are more slant path signal with low elevation angle coming in, the extended grid model can achieve better results, otherwise the fundamental regular one can get tomography results with higher precision since there are more unknown voxels and no improvement for SWD structure for the extended grid model. In a word, for SH region, the fundamental regular grid model can get best tomography results.