Abstract: Combined with the operation performance of direct fired heater through analyzing the components of soot exhausting of the heater, a special technology designed to combine two-class dedusting with desulfurzing by circulating fluid bed is adopted. The system is able to ensure the sufficiency of desulfurizing and dedusting, and ensure the fume emission meeting the needs of relative environmental protection standards simultaneously. The application of the desulfurizing and dedusting system shows that the desulfurzing technology achieves a anticipated goal in environmental protection, which solves actual productive issues.