Abstract: The modified Dubinin-Astakhov approaches,which are based on the experimental data to define the pseudo-vapor pressure for substituting the p_s term in the Dubinin-Astakhov equation,cannot give the clear physical meanings to the predicted results.A new equation,based on the lattice theory,is developed to describe the supercritical fluid adsorption inside the slit-pores of micro-adsor bents.The analytical solution to the equation is applied to predict the supercritical high-pressure hydrogen adsorption inside the pores of the adsorbents.The prediction emphasizes on the fluctuations of the excess adsorption as a function of the bulk density of hydrogen in reduced units over the temperature range 77～298 K and for the pressure up to 30 MPa.The results from the equation are compared with the experimental results and those from the GCMC molecular simulation. It shows that the new equation can elucidate the peculiar features in adsorption isotherms of supercritical fluids which are fundamentally different from those of the standard（IUPAC）classification,and the results from the equation can also qualitatively reflect the experiment results.