Poly-silicon deposition rate profiles on silicon wafers were evaluated along the axial direction and radial direction in a mass-production scale low-pressure chemical vapor deposition (MPS-LPCVD) reactor using SiH4. Numerical analysis was made by computational fluid dynamics (CFD) considering coupled chemical reactions at several temperatures around 873 K. We have performed elementary reaction simulation, which includes 19 chemical species and 33 reactions. Despite the complexity of the chemical reaction process of poly-silicon film deposition, we could conclude that Si deposition rate was mainly controlled by the surface reaction of SiH4 under LPCVD condition. The contributions of chemical species formed in the gas-phase could be ignored. Thus, we successfully simulated the experimental results with a simplified 2-step surface reaction model of SiH4. Predicted film thickness along the axial direction of the reactor agreed well with experimental results, and the 2-step reaction model proved to be a good tool for the numerical simulation of the poly-silicon deposition process in an MPS reactor.