Considering the hydrostatic pressure, the spontaneous and piezoelectric polarization, the dielectric mismatch, and 3D confinement of the electron and hole, the exciton states and interband optical transitions in -oriented wurtzite InxGa1-xN/GaN strained coupled quantum dot (QD) nanowire heterostructures (NWHETs) have been investigated by using the effective mass approximation, the simplified coherent potential approximation, and a variational approach. Our results show that the hydrostatic pressure, the strong built-in electric field (BEF), and the dielectric mismatch have a significant influence on the exciton states and interband optical transitions. The exciton binding energy increases almost linearly with the hydrostatic pressure for a given QD NWHET. The emission wavelength has a blue-shift (red-shift) if the hydrostatic pressure (QD height or the potential barrier thickness) increases. Our calculations also indicate that the radiative decay time has a quick increase with increasing of the QD height and the barrier thickness. The radiative decay time decreases if the hydrostatic pressure increases. The BEF (dielectric mismatch) dramatically decreases (increases) the exciton binding energy. The physical reason has been analyzed in depth.