The morphological change of Dubinin-Radushkevich (DR) plots of the N-2 adsorption isotherm for graphite slit pores was examined with relevance to the pore size distribution (PSD) and the temperature dependence using grand canonical Monte Carlo (GCMC) simulation. The simulated DR plots with different half-widths of PSD having Gaussian and Gaussian-like distributions of average pore width = 1.2 nm were almost the same as each other below [ln(P-0/P)](2) = 60; the Linearity depending on the half-width of PSD was observed over the [ln(P-0/P)](2) range of 10-60. On the other hand, the DR plot deviated downward from the linear relation seriously above [ln(Po/P)](2) = 60. This is caused by adsorption in the pore for pore widths less than 1.0 nm. The micropore volume calculated from the DR plot for pore widths more than 1.6 nm is underestimated considerably, but that for pore widths less than 1.4 nm is reasonable. The higher the adsorption temperature, the narrower the linear region of the DR plot. The limitation of the Dubinin-Astakov plot is appointed.