Numerical modeling of salinity changes in marine environment of Persian Gulf is investigated in this paper. Computer simulation of the problem is performed by the solution of a convection-diffusion equation for salinity concentration coupled with the hydrodynamics equations. The hydrodynamic equations consist of shallow water equations of continuity and motion in horizontal plane. The effects of rain and evaporations are considered in the continuity equation and the effects of bed slope and friction, as well as the Coriolis effects are considered in two equations of motion. The cell vertex finite volume method is applied for solving the governing equations on triangular unstructured meshes. Using unstructured meshes provides great flexibility for modeling the flow problems in arbitrary and complex geometries, such as Persian Gulf domain. The results of evaporation and Coriolis effects, as well as imposing river and tidal boundary conditions to the hydrodynamic model of Persian Gulf (considering variable topology rough bed) are compared with predictions of Admiralty Tide Table, which are obtained from the harmonic analysis. The performance of the developed computer model is demonstrated by simulation of salinity changes due to inflow effects and diffusion effects as well as computed currents.