This paper presents a Stratified Three zone Diesel Combustion Model consisting of “No. 1-burning zone,” “No.2-burned zone,” and “No.3-low temperature air zone,” based on the hypothesis proposed by one of the authors (Matsuoka)(1) (2) (3). This hypothesis accounts for the re-entrainment of its own burnt gas (REOBG) into the diesel spray flame. The air from zone 3 is entrained into zone 1 and zone 2, where it is partially entrapped by zone 2. The burned gas of zone 2 also re-entrains and mixes in zone 1 forming each stratified layer. Parametrical study results compared with the measured data show that such entrainment has a significant physical effects on the main combustion phase. As a result, it causes a drop in the acceleration rate of heat release, also an increase of pyrolyze that in turn promotes the soot formation. Chemical reactions caused by this REOBG that appears in the later combustion stage are also considered.