A novel quasi-thermodynamic approach is suggested to simulate surface chemistry in III-V compound MOVPE. Blocking of free adsorption sites by methyl radicals is considered as the mechanism limiting the growth rate at low temperatures. This assumption has provided a good reproduction of experimental data on GaAs MOVPE in various types of reactor. The commercial computational fluid dynamics software CFD-ACE™ has been used to perform a detailed threedimensional modeling of AlGaAs and InGaP deposition in an AIX-200 horizontal reactor. The surface model has been incorporated into the code to obtain the growth rate and layer composition distributions over the substrate. Modeling results demonstrate a reasonable agreement with experimental data.