Antimonide-based optoelectronic devices are pivotal for compact, high-efficiency light sources in the 2~4 μm mid-infrared range, driving advancements in gas sensing and laser medical technologies. The rapid development of novel antimonide lasers, however, faces a critical bottleneck: the lack of experimental data on strain-induced band offsets in key structures like InGaSb/AlGaAsSb quantum wells, which is essential for accurate device design. This study addresses this gap by employing a combined approach of Deep Level Transient Spectroscopy (DLTS) and Photoluminescence (PL) to experimentally determine the band discontinuities in such quantum wells. High-quality epitaxial wafers, verified by atomic force microscopy, high-resolution X-ray diffraction, and PL for surface morphology, crystallinity, and emission wavelength, were processed into lasers. Packaged devices were characterized for P-I-V curves and lasing wavelength before undergoing DLTS in a high-vacuum (1×10E-5 Torr), variable-temperature (85K~300K) system with a high-sensitivity capacitance meter (0.01 fF, 2 μs sampling). Our core innovation lies in directly measuring the conduction band offset via DLTS to be 0.352 eV. Combining this with the PL-determined transition energy yielded a valence band offset of 0.156 eV. Beyond band offsets, DLTS revealed critical defect properties: a minority carrier peak was identified as electron traps in the waveguide layer (capture cross-section: 1.7~3.0E-14 cm²; density: 2.90~2.95E18 cm^-3). A majority carrier peak near 150 K (activation energy: 0.13 eV; capture cross-section: 1.9~2.2E-16 cm²; density: 2.71~4.26E18 cm^-3) is attributed to hole emission from the quantum wells. This work provides the first direct experimental determination of critical band parameters and simultaneously characterizes key defect states, furnishing indispensable data for band engineering and defect suppression in next-generation antimonide lasers.