The CO2 gas dissolved fuel for the diesel combustion is effective to reduce the NOx emissions to achieve the internal EGR (Exhaust Gas Recirculation) effect by fuel. This method has supplied EGR gas to the fuel side instead of supply EGR gas to the intake gas side. The fuel has followed specific characteristics for the diesel combustion. When the fuel is injected into the chamber in low pressure, this CO2 gas is separated from the fuel spray. The distribution characteristics of the spray are improved and the improvement of the thermal efficiency by reduction heat loss in the combustion chamber wall, and reduce soot emissions by the lean combustion is expected. Furthermore, this CO2 gas decreases the flame temperature. Further, it is anticipated to reduce NOx emissions by the spray internal EGR effect.In this paper, the n-tridecane and CO2 gas were used as a basic fuel spray research, and shadowgraph photography and luminescence flame photography were conducted to measure the evaporation characteristics and flame characteristics of the fuel spray. In addition, chemiluminescence photography and luminous flame photography were conducted in the RCEM (Rapid Compression and Expansion Machine) for the combustion characteristics. Effervescence of CO2 gas improves evaporation of the spray, and it promotes air-fuel mixture formation. The temperature and KL factor become lower with the increase in dissolved pressure. The simultaneous reduction of NOx and soot can be achieved by use of the CO2 gas dissolved fuel.