In order to deeply understand the physical properties of strained heterojunction quantum well structures and improve the design of wide-bandgap nitride semiconductor devices, in this paper, based on the six-band stress-dependent k·p Hamiltonian and the self-consistent Schrodinger-Poisson equation, the valence subband model of wurtzite GaN/AlN quantum well with polar (0001) , semi-polar ( $10\overline{1}2$) and non-polar ( $10\overline{1}0$) orientations under field confinement was established. The subband energy dispersion relations between GaN/AlN quantum well with different crystal orientations under biaxial and uniaxial stresses were also given. According to the influence of stress on the valence band structure of quantum well, the microcosmic physical relationship between stress and hole effective mass was studied comprehensively. The results show that the valence band structure heavily depends on the modification in crystal orientation. The biaxial stress has little effect on the improvement of effective mass. However, uniaxial compressive stress can obtain more holes in the region of low effective mass by reducing the energy in the vertical channel direction, such that the hole effective mass can be effectively reduced. And it is reduced by about 90% in the structure of different crystal orientations.