Ribulose 1, 5-bisphosphate carboxylase-oxygenase (RuBisCO), a Calvin cycleenzyme, is responsible for absorbing the majority of atmospheric CO2 intophotosynthetic organisms. RuBisCO has been the subject of a great deal of researchover the years, but its progress is still constrained by the low activity of theRuBisCO enzyme. It has not yet been documented how tightly bound inhibitorsinduce decreased efficiency and how this is related to CO2. In this research, themolecular dynamic simulation technique was used to investigate the binding ofcarbon dioxide at different optimal pH of the enzyme and the results were comparedwith the laboratory results at pH=8.0, which were at pH 7.5 and 8.2. The obtainedresults were close to the laboratory results.Keywords: Calvin cycle, CO2 fixation, Optimal pH, RuBisCO