The objective of this study is to investigate the relationship of performance of the captioned engine and its characteristics of exhaust emission and conclusively to systematize the combustion analysis of it. As a first step, the burning rate and other several combustion characteristics values are obtained from the statistical values from the pressure-cards of a number of cycles, and their correlation with the IMEP, ISFC, ISNO, exhaust temperature and cyclic variation of combustion are determined, being employed the connection orifices and air fuel ratios as parameters. By deducing from their results, the following new concept is obtained that it should be introduced into the analysis of the combustion phenomena of this type of engine, that is to renew the past concept of two staged combustion system but this is three staged combustion engine. And a guiding principle for further study of this type of engine is established.1. The first stage combustion at prechamber has the role of igniting the lean mixture of main chamber and that of the ejection of the jet flame for accelerating the combustion of main chamber.2. The second stage combustion occurs during the first-half combustion period of main chamber by means of flame jetting combustion. The flame jet involves a great amount of the mixture of main chamber within a short period. An increase of this component causes a significant increase in heat loss than thermal efficiency, resulting in a worsening IMEP, ISFC, and furthermore an increase in ISNO.3. The third stage combustion occurs during the later-half combustion period of the main chamber by means of the diffusive propagating combustion. The flame jet, impinged on the surface of the wall after the second stage combustion, is converted into small swirls and turbulences, which accelerate the combustion of the unburned mixture in the main chamber. When this component is increased, IMEP and ISFC are improved without heat loss and ISNO showing any significant increase.4. The deeper investigation of each role of three stage combustion mechanism should be emphasized. Thereby, the optimization of each component of this type of engine will be improved and the capability and ultimate limit of performance characteristics of it will be defined.