China is developing a new type of slurry-feed membrane wall entrained flow gasifier with two-stage oxygen supply in order to improve facility availability and efficiency. Detailed modeling can contribute to obtaining an in-depth understanding of the gasifier and achieving optimal design and operation. In this work, a computationally efficient reactor network model was developed. Available industrial data from a single-stage version of this type of gasifier was used to validate the model. Good agreement was observed in carbon conversion, syngas composition, and steam production in the membrane wall, suggesting that the model was able to provide accurate prediction, including gasifier outlet parameters and internal heat transfer rate. The impact of the five most important parameters on the gasifer performance-the location of second-stage oxygen injectors, the fraction of the second-stage oxygen in total oxygen fed to the gasifier, the thickness of the refractory lining on the membrane wall inner surface, the water tube diameter, and the width of the fins which links the tubes-was investigated. Optimized design and operation guidelines for improving operational economy and availability were provided.