We have theoretically investigated the optimized quantum well structure for the ultra-deep ultraviolet (UV) AlGaN light emitting diodes (LEDs) with the consideration of band structure deformation caused by polarization effect. In this paper, we further employ an asymmetric active region to reduce the polarization field in the well-barrier interface and modify the band structure to enhance the power efficiency of the AlGaN LED. By increasing the thickness of p-side barrier from 5 nm to 15 nm, the deformation slope of energy band in the well region is reduced due to the reduction of polarization field, which is caused by the large polarization charges in the interface of p-side barrier and carrier blocking layer. Accordingly, the hole concentration is increased and the carrier distributions are more uniform caused by the less-tilted energy band in the well. Therefore, a higher recombination rate and a higher output power can be obtained. Moreover, the power efficiency of AlGaN LED is barely related to the n-side barrier thickness due to the less polarization field. However, a thinner n-side barrier is preferred to enhance the current spreading. Therefore, an asymmetric QW with a thinner n-side barrier and a thicker p-side barrier is a better choice to enhance the power efficiency for the deep UV AlGaN LED.