This paper is concerned with the temperature uniformity control of a furnace system with multiple burners and multiple parallel passes, which is commonly used in the petroleum refinery industry. In order to maintain the furnace system running in a safe, stable, and high-efficiency state, it is necessary to control the outlet temperature difference among multiple parallel passes. In this paper, a fuzzy control scheme based on the difference control technique is introduced to keep the uniformity of the outlet temperatures of the multiple parallel passes, a multi-input multi-output (MIMO) fuzzy controller design is investigated and demonstrated, the application result of the proposed control approach to a petroleum refinery furnace system shows that it is effective.