In order to study the slagging characteristics of waste incinerator walls, three pieces of slag were collected on site from the front arch wall, rear arch wall and side wall in the throat area. The ash fusion point tester, scanning electron microscopy (SEM)/ energy dispersive X-ray(EDX), and X-ray diffractometer(XRD) analytical methods were used to determine the melting characteristics, microscopic morphology, element distribution, and phase composition and other physical and chemical properties of slag samples of slag. For the layered slag samples, elemental analysis and phase analysis were carried out along the growth direction of the slag. The results show that the difference in the characteristic temperatures of the three slag samples is small, and the softening temperature is less than 1 260 ℃, all of which are easy to slagging. The micromorphology of the three slag samples are similar through scanning electron microscope, mainly rock particles, indicating that the ash particles directly adhere to the furnace throat wall or slag surface without melting and spheroidization. The distribution of K, Na, and Al in the slag sample is similar, and the three elements gradually decrease along the slag growth direction。The K、Na and Al form three feldspar substances, such as KAlSi3O8 with a melting point of 1 130 ℃, KAlSi 2O6 with a melting point of 1 100 ℃, and NaAlSi3O8 with a melting point of 1 100 ℃. The three low-melting feldspars are viscous after melting and are easy to deposit on the wall or slag surface. Along the growth direction of the slag sample, the content of the Ca gradually increases, and the Si/Ca is 0.8-1.1. Through the XRD, it is found that Si and Ca form the Ca2MgSi2O7, which is the most important substance in the slag sample with a melting point of 1 450 ℃. The high melting point of Ca2MgSi2O7 determines that only when the slag grows to a certain thickness, the outer surface of the slag begins to melt, which can prevent the slag from continuing to grow.