Abstract: Reasonable proportion of the mid-pumparound heat is one of the effective measures for energy saving and consumption reduction for the atmospheric and vacuum distillation unit. The deep analysis of the mid-pumparound heat theory was performed and the process simulation software（Pro/II） was used to simulate a 3.6 Mt/a atmospheric column of a refinery，revealing the effect of mid-pumparound heat on product yield of the distillation column. The theoretical explanation was given for the cause of this impact. Based on the research results of predecessors and comprehensive consideration of various factors，the relevant principles of the optimization of the mid-pumparound heat were proposed，which provided a basis for the stable operation，the regulation of production schemes and energy saving of the unit.

Key words: energy saving and consumption reduction, mid-pumparound, product yield, heat distribution, optimization principle