A new approach to realize ultraviolet (UV) light emitting diodes (LEDs) is using AlN/GaN or AlxGa1-xN/GaN SL structure as active layers. Effect of a uniaxial strain on the degree of polarization (DOP) of Al0.26Ga0.74N/GaN superlattices (SLs) grown on c-plane sapphire substrates has been investigated. Compared with AlN/AlxGa1-xN quantum wells, the DOP of the light emission from Al0.26Ga0.74N/GaN SLs shows an opposite variation tendency with in-plane strain and quantum confinement. The results would be helpful to the structural design of c-plane deep-UV and UVA LEDs to enhance surface emission.