Membrane wall entrained-flow gasifier (MWEFG) generally has a long service life for the protection of the solid slag layer adhered to the metal wall during operation. However, cracking will generate in the slag layer when the temperature changes greatly in the gasifier, which results from the thermal stress exceeding the strength of slag deposit. In this study, the gasification experiment was performed in a bench-scale MWEFG and a three-dimensional model was developed for non-steady thermal stress analysis of slag layer. Based on experimental data, the thermal stresses of cooling process were numerically simulated using transient thermal analysis. The results indicate that the thermal stresses of the slag layer are tensile during the cooling and the Von Mises stresses (SEQVs) increase with the reduction of temperature. Comparing the results of the selected nodes, it is found that the SEQV always increases from the slag surface to the slag-SiC interface. The contributions of slag porosity and thickness were also investigated. We draw a conclusion that the maximum SEQV decreases with the increasing porosity, while it increases with the increasing slag thickness. (c) 2011 Elsevier Ltd. All rights reserved.