Meta boric acid which can be used in the esterification for the control of liquid oxidation of n-paraffin was obtained by dehydration of ortho boric acid. The characteristics of dehydration or ortho boric acid and effects of the experimental variables on the conversion of ortho boric acid to meta boric acid were examined in order to obtain the basic data which are required for the design and scale-up of process producing meta boric acid. Particle size, reaction temperature and pressure, particle content in the slurry phase, mixing speed and reaction time were chosen as operating wvariables, and the reaction was analyzed in terms of a heterogeneous liquid-solid reaction model. From the results of this study, the diffusion in the particle was presumed as the rate determining step, and the optimum conditions for this reaction were determined as follow in view of economics : t(reaction time_:35-40min, T(reaction temperature):135-140℃, R(mixing speed):700-800rpm, S(slurry content)25-28wt%, d_p(particle size):0.20-0.35mm, P(reaction pressure):700-720mmHg.