In the production of boron fibers using CVD technique, boron deposition and dichloroborane formation reactions take place in a reactor. Boron deposition reaction occurs at the surface while formation of dichloroborane is the result of both gas phase and surface reactions. A CSTR type of reactor was designed and constructed from stainless steel to investigate the gas phase reaction kinetics and kinetic parameters of boron fibers produced from the reaction of boron trichloride and hydrogen gases in a CVD reactor. The gases were heated by passing through the two pipes which were located into the ceramic furnace and they were mixed in the CSTR. The effluent gas mixture of the reactor was quenched by passing through a heat exchanger. An FT-IR spectrophotometer was connected to the heat exchanger outlet stream to perform on-line chemical analysis of the effluent gas mixture. Experiments were carried out at atmospheric pressure and a reactor temperature range of 300-600 &ordm / C with different inlet reactant concentrations. The analysis of the FT-IR spectra indicated that the gas phase reaction and the surface reaction started at reactor temperatures above 170 &ordm / C and 500&ordm / C, respectively. It was concluded that reaction rate of the product increased with an increase in the inlet concentration of both reactants (BCl3 and H2) and with an increase in the reactor temperature. The gas phase reaction rate was expressed in terms of a th and b th orders with respect to the inlet concentrations of BCl3 and H2. The activation energy of the gas phase reaction, a and b were found to be 30.156 , 0.54 and 0.64, respectively. The correlation coefficient was 0.9969.