Analysis and simulation studies of the longitudinal mode behavior of two-section coupled-cavity lasers in the steady-state are presented. The laser is analyzed with a resonance amplifier model and the scattering matrix formulation. The mode selection property of this laser is explained in terms of the wavelength-dependent effective reflectance. Expressions for the effective reflectance and the mode power are derived for two different cases: the case of weak reflection from the junction and strong coupling between individual cavities, and the case of strong reflection at the junction and relatively weak coupling between cavities. It is shown to be possible to simulate the longitudinal mode behavior with respect to temperature changes and wavelength tuning by separately pumping each section of the laser.