Abstract: Fixed-bed gasification has low gas heat value, low gasification efficiency, small fuel scope and complex pretreatment at room temperature. The influence of different preheated air temperature and excess air coefficient for municipal solid waste in a small, rotary kiln pyrolysis gasifier was studied with the control variable method. The result showed that the preheated air temperature rising is helpful for pyrolysis and gasification, but there are some limitations. When the temperature exceeded 600 ℃, the garbage gasification gas decreased obviously. The garbage reached the maximum value and gasification efficiency and minimized the tar yield when the excess air coefficient was 0.4. The heavy metal contents in slag, fly ash and garbage were investigated at the conditions of excess air coefficient 0.4 and air preheating temperature 500 ℃. The lead content in fly ash was much higher than the value in GB 18598-2001 Standard for Pollution Control on the Security Landfill Site for Hazardous Wastes, indicated a need for processing before being emitting. Dioxin sampling analysis results were below the value in GB 18485-2014 Standard for Pollution Control on the Municipal Solid Waste Incineration. The results showed that the best excess air coefficient of the rotary kiln pyrolysis gasification process was 0.4, and the optimum air preheating temperature was 500 ℃. Under the optimum conditions, the tar production, fly ash and coke slag heavy metal content was small, and dioxin levels were less than 0.1 ng/m³.