And it is calculated and analyzed the distribution and quantity of slag thermal stress created by boiler load shift . thermal stress quantity can be as big as e / 1000 and is enough to destroy slag structure and to make some drop . it is also concluded that the walltube parameters can only affect on thermal stress of the slag that is near to contact surface and contribute little to slag drop 针对锅炉变负荷运行时炉膛的自然掉渣现象，分析锅炉水冷壁渣层中热应力的产生机理，建立了水冷壁渣层热应力的计算模型，计算分析了锅炉大范围变负荷运行产生的渣层热应力变化大小和分布，并分析渣层热应力的影响因素。
