A combined system of flow injection/hydride generation coupled with multichannel plasma spectrometer was put forward and applied to the simultaneous determination of trace arsenic and mercury. The interface between flow injection hydride generation (FI-HG) and ICP-AES, gas/liquid separator and main experimental parameters were described. The detection limits of the proposed method could be achieved to 0.x μg/L level; The RSD 1.4% and 1.3% at 10 ng/mL levels of As and Hg respectively. The frequency of sampling was 150/h with 80μL sampling volume. The proposed method has been applied to the simultaneous determination of As and Hg in some real samples.