Abstract: The industrial production of H₃¹⁰BO₃ (¹⁰B>19.8%) requires monitoring the extent of the reaction and determining the endpoint of the reaction. In order to solve the problems of complicated steps, large human error and low accuracy of the existing monitoring methods, an experimental device for on-line monitoring the progress of the reaction was designed and built, and the experiment of H₃¹⁰BO₃ prepared by the reaction of ¹⁰B-enriched boron trifluoride (¹⁰BF₃, ¹⁰B>19.8%) and strontium carbonate (SrCO₃) insoluble in water (H₂O) was monitored in situ, in real time and on-line by using this experimental device. The data curves of the ion concentration of the solution changing with time obtained by the test can be fitted by the formula of c_t−c₁=c₀e^−kt, and the fitting coefficient R² is 1.000 00. Under the same conditions, four data curves of the ion concentration of the solution changing with time are fitted by the formula of c_t−c₁=c₀e^−kt, and the fitting coefficient R² are all equal to 1.000 00. The long-term and repeated test results of this experimental device indicate that the obtained data has high accuracy, small error, and good reproducibility. The standard deviations (s) of the three parameters of c₁, c₀ and k of the fitting equation are all less than 0.3%, which shows that the fitting precision of c_t−c₁=c₀e^−kt equation is high. The equation of c_t−c₁=c₀e^−kt can be used to monitor the progress of the reaction of preparing H₃¹⁰BO₃ from ¹⁰BF₃. The fitting equation c_t−c₁=c₀e^−kt of the data curve of ion concentration changing with time obtained from the experiment is consistent with the first-order kinetic equation of c_t=c₀e^−kt of chemical reaction, which shows that the progress of the reaction of preparing H₃¹⁰BO₃ by fitting ¹⁰BF₃ with c_t−c₁=c₀e^−kt equation is in line with the essence of chemical reaction, and the equation c_t−c₁=c₀e^−kt can be used as ¹⁰BF₃ to prepare H₃¹⁰BO₃. The most reasonable feeding method for preparing H₃¹⁰BO₃ from ¹⁰BF₃ is that insoluble solid powder SrCO₃ and H₂O are mixed and stirred to form a suspension, then the suspension is heated to a set temperature and kept constant, and then ¹⁰BF₃ is added to the suspension. The on-line monitoring results show that the preparation of H₃¹⁰BO₃ from ¹⁰BF₃ requires three steps of defluorination hydroxyl substitution reaction, in which the first two steps of defluorination hydroxyl substitution are fast reactions, and the third step of defluorination hydroxyl substitution is slow reactions, that is, the third step of hydroxyl substitution reaction is the rate control step of the preparation of H₃¹⁰BO₃ from ¹⁰BF₃. The reaction of preparing H₃¹⁰BO₃ from ¹⁰BF₃ is an apparent chemical first-order kinetic reaction.