Learning the nature of formation water helps us evaluate the prospects of oil as well as identify oil and water reservoirs. Among the ions in the composition of the formation water, bromide and iodide are two important elements which reflect the environment and the degree of mineralisation and reservoir closure. The authors focus on determining the concentration of bromide and iodide in the formation water using the spectrophotometric method (UV-Vis). This method was mentioned in the "Standard Methods for Water and Wastewater", however, it was applied in formation water analysis for the first time in Vietnam. The method allows a low detection limit of 0.1 mg/L, with the reproducibility of 10 sample analysis and the deviation in comparison to 10 samples in control experiments being lower than 5 percent. The results are verified with other laboratory's ones and thereby allow a wide use in formation water analysis.