The effects of the nonequilibrium population of optical phonon (hot-phonon effect) and acoustic phonon (self-heating effect) on the dc performance of carbon nanotube (CNT) MOSFET are examined by solving coupled semiclassical electron and phonon transport equations. In this paper, the numerical solution of these coupled transport equations is described. Full-band electron and phonon Boltzmann transport equations are solved to simulate the electron and phonon transport. Electron-phonon scattering rates are calculated using the tight-binding approach and the phonon-phonon scattering by relaxation time approximation (optical phonon relaxation time extracted by fitting the measured data of metallic tube). We show that the dc ballisticity of a CNT MOSFET degrades by approximately 10% due to hot-phonon effects, which is a much smaller degradation compared to two-terminal measurement of metallic tubes. Self-heating of the tube is also examined and is found to be insignificant for a single-tube transistor.