This paper presents and compares the mathematical models and computational fluid dynamics (CFD) models for degassing of oxygen from water in a laboratory-scale multi-function gas-liquid contactor under various operating conditions. The optimum correlations of the overall volumetric liquid-phase mass transfer coefficient (kLa) are determined by the mathematical models of specific contactors. Both the continuous-reactor model and semi-batch model can evaluate the degassing efficiency with relative errors within ±13%. Similarly, CFD models agree with experimental data with relative errors of ±10% or less. Overall, the mathematical models are deemed easy to use in engineering practice to assist the selection of efficient contactors and determine their optimum operation parameters. The CFD models have a wider applicability, and directly provide the local mass transfer details, making it appropriate for harsh industrial scenarios where empirical correlations for important quantities are unavailable. Combining these two types of models can effectively guide the design, optimization, and operation of the high-throughput degassing system.