The concentration of selenium in grain samples was determined using isotope dilution method in ORC-ICPMS. The experimental conditions were optimized to $H_2$ mode and the flow rate was $4.0;mL;min^{-1}$. ORC in $H_2$ mode proved to eliminate most of polyatomic interferences except $BrH^+$ when Br is present in sample matrix. Chemical removal of Br was very difficult and the mathematical correction was successfully employed. The fraction of $BrH^+$ generated from Br at the current experimental condition was 14.1%. The signal on m/z 82 was corrected and calculated for isotope dilution. The analytical reliability of the propose method was successfully evaluated by analyzing the certified standard reference material NIST SRM 1566 and 1567. The method was applied to real samples and the results are $0.034{pm}0.001;{mu}g;g^{-1}$ for white rice, $0.059{pm}0.002_5;{mu}g;g^{-1}$ for brown rice, $0.029{pm}0.001_4;{mu}g;g^{-1}$ for black rice, and $0.034{pm}0.002;{mu}g ;g^{-1}$ for barley. The detection limits ($3sigma$) for Se was $0.012;ng;g^{-1}$.