At present, the detection of selenium (Se) is mainly carried out by hydride generation -atomic fluorescence spectroscopy (HG-AFS). It has been found that the sensitivity of Se can be improved by using the interval hydrogen generator to provide the hydrogen (H2) for HG-AFS. When the H2 flow rate reaches 80 mL·min-1 and above, the H2 provided by the hydrogen generator can ignite the hydrogen flame first, effectively avoiding the influence of ignition early or delay on the measurement, which can improve the precision of the measurement. In geochemical surveys, dozens of elements need to be detection, and they also needs to perform multiple digestions separately. Se, as one of the elements, is digested with nitric acid (HNO3)-perchloric acid (HClO4), after the digestion, Se(Ⅵ) will be reduced to Se(Ⅳ) by concentrated hydrochloric acid (HCl). According to DZ/T 0279.3—2016, when using inductively coupled plasma mass spectrometry (ICP-MS) to determine 15 elements such as barium (Ba), beryllium (Be) and bismuth (Bi), the samples are digested with HNO3-HF-HClO4 and then dissolved in aqua regia. It was found that Se in geochemical samples is more completely digested with HNO3-HF-HClO4, and at large number of chloride ions (Cl-) contained in aqua regia can reduce Se(Ⅵ) to Se(Ⅳ). Therefore, only one digestion is needed and then detect Se by HG-AFS as well as other 15 elements using ICP-MS separately. Based on the above research results, this method for determining Se in geochemical samples by H2-HG-AFS has a detection limit of 0.007 mg·kg-1, and a precision (n=12) of 2.1% to 5.3%. According to the established method, 36 soil and water sediment standard materials were selected to analysis, the relative error was between -13.61% to 16.9%, and most of the errors were within ±10%, which achieved very satisfactory results.