From the starting point of the master equation for particle diffusion in a lattice with site-energy disorder, we study the mobility and collective diffusion of lattice gases within it. The explicit expressions for the mobility and collective diffusion coefficients are derived under an approximation. The numerical calculation of the collective diffusion coefficient of the lattice gases on a linear chain with a dichotomous distribution of site energies is finished. It is found that our numerical result is in reasonable agreement with the results of computer simulations.