Several factors effect on choosing the best enhanced oil recovery process in a hydrocarbon reservoir. In the present study, effective factors on chemical enhanced oil recovery involved in polymer flooding, surfactant flooding, surfactant-polymer flooding, and alkaline-surfactant-polymer flooding are discussed in numerical simulation. The numbers of the simulation runs are estimated based on the number of factors and their maximum and minimum values using experimental design software. Oil recovery factor from reservoir simulation is considered as comparison factor in all of the run cases. The results from one parameter and two interaction factors during each flooding case were analyzed by Tornado and Parto plot. The oil recovery factor also was estimated using statistical analysis using Minitab. The results show that there is a strong correlation between simulation and statistical analysis. Furthermore, the results show that each selected factor has a different effect on oil recovery in each case of chemical flooding. The case study results on two Iranian oil fields at the end of the present study clarified that results of this study can be useful for selecting the best chemical process for oil reservoir based on reservoir properties.