The research prepared two deep ultraviolet (DUV) AlGaN-based multiple quantum well (MQW) samples with the same Al content in the QWs but different well widths (3 nm for Sample A and 2 nm for Sample B). Photoluminescence (PL) measurements reveal that Sample A exhibits only one main PL peak across all measured temperatures, while Sample B displays one main PL peak at low temperatures and two distinct PL peaks at high temperatures. Furthermore, compared with Sample A, Sample B exhibits a more significant temperature-dependent PL peak wavelength blue shift relative to the Varshni curve, a more significant excitation power density-dependent PL peak blue shift accompanied by linewidth broadening, as well as a larger non-radiative recombination related activation energy and higher internal quantum efficiency (IQE). These findings can be explained by the observation that the narrower well width of Sample B induces a more pronounced effect of carrier localization than the wider well width of Sample A, due to the enhanced fluctuation in well width and reduced quantum-confined Stark effect (QCSE).