The invention discloses an on-line analysis pretreatment system of a sulfur-burning sulfuric acid incinerator sample. The system comprises a sample sampling probe and a filter system, wherein the filter system comprises a compression refrigerator, a paper filter, a paraffin wax cleaning filter, a glass bead filter, a fiber filter, and a hydrophobic membrane filter, which are sequentially connected through pipelines and a plurality of valves, the sampling probe is connected with the compression refrigerator through a pipeline, the hydrophobic membrane filter is connected with an analysis meter through a pipeline with a flow meter, and a temperature setter is arranged on the compression refrigerator. By adopting the above structure, the sulfur-burning sulfuric acid incinerator sample is firstly cooled, dedusted and dewatered by the compression refrigerator and a visual observation tank, and then enters into the paper filter, the paraffin wax cleaning filter, the glass bead filter, the fiber filter and the hydrophobic membrane filter, so as to ensure that the temperature, the water content, the acid content and the dust content of the sulfur-burning sulfuric acid incinerator sample which is subjected to multi-stage cooling, dewatering and dedusting filtration, can meet requirements before entering the analyzer.