Reactivity controlled compression ignition (RCCI) is a new COMBUSTION model in which a mixture of fuel inside the cylinder is provided by injection of low reactivity fuel in the fuel inlet manifold and multi-stage injection of high reactivity fuel inside the cylinder. By changing the engine input parameters and determining the conditions, this study attempted to approximate a biodiesel dual-fuel (C11H22O2) / natural gas engine to the COMBUSTION phase of reactivity controlled compression ignition (RCCI) to examine and compare the efficiency and output emissions. The understudy influencing factors included the comparison between the biodiesel-natural gas and diesel-natural gas fuels with similar energy generation, relevant strategies, and fuel emission rate. In this research, the 3401E Caterpillar engine geometry was employed for the numerical simulation by the commercial Converge Software and SAGE COMBUSTION model. The results showed that, due to the high Cetane number and high oxygen present in its composition, the biodiesel fuel gave rise to earlier COMBUSTION as compared with diesel. The injection time precession, shortened injection time, and increased injection rate in the first phase increased pressure, average temperature, and the heat release rate, and the power and yield of COMBUSTION enhanced. Likewise, due to complete COMBUSTION, the rates of output emissions, including CO2, HC, and soot, decreased.