Abstract: Boron in oil field water has been directly determined by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) after sample were treated with nitric acid and filtrated. This method overcomes the problems of spectrophotometry such as long analysis flow, more reagent and difficulty in controlling the chemical procedure. The working parameters and the spectral line were optimized by orthogonal tests. The dilute multiple and acid medium were analyzed using the selected 208.959 nm frequency. The results show that it is not necessary to dilute the sample when the content of B is less than 10 mg/L, and the dilution factor is 20 when B is greater than 10 mg/L. The selected HNO₃ as the acid medium, improved the accuracy of the results. The interference tests were carried out for 7 major metals in oil field water. 20 mg/L Sr, Ba and Fe, 50 mg/L Mg and Ca, 100 mg/L K and 200 mg/L Na have no interference for the measurements of the target element. The detection limit of boron was 0.0020 mg/L and the recoveries ranged from 95.3％ to 102.0％ with a precision in the range of 0.43%~0.92% (RSD, n=11). Compared to the method of curcumin spectrophotometry, this method is simpler and faster and the results are more accurate.