We present an attempt to clarify the valence band order of ZnO and MgxZn1−xO films grown by pulsed laser deposition (PLD) on sapphire substrates. We derive the dependence of spin orbit interaction (Δso) and crystal field interaction (Δcf) on the temperature, strain and cation replacement (Zn with Mg) and compared this with theoretical predictions. The strain was varied by using different orientated sapphire substrates (c-, r-, and m-plane orientations) and by varying the film thicknesses. All these investigations support the conclusion that the symmetry order of the valence band is Γ7-Γ9-Γ7 for ZnO and MgxZn1−xO for x ≤ 0.55.