A simple, inexpensive, and sensitive method was developed for the determination of inorganic arsenic species As(III), As(V) and total arsenic in environmental water samples using multiwalled carbon nanotubes (MWCNTs) as solid phase extraction (SPE) adsorbents coupled with hydride generation atomic fluorescence spectrometry (HG-AFS). The procedure is based on selectively absorbance of the chelates of As(III)-ammonium pyrrolidine dithiocarbamate (APDC) on the MWCNTs at pH range of 2.0-5.0, while As(V) was passed through the microcolumn. The retention complexes of As(III)-APDC was eluted completely with 3 mL of 2.0 mol L-1 HCl solution at a flow rate 1.0 mL min-1, and then directly determined by HG-AFS. The effluent of As(V) was determined using thiourea and ascorbic acid as reducing agent for reduce As(V) to As(III). The different parameters that control the preconcention/separation step of As(III) and As(V) and determination have been investigated in detail. Under the optimized conditions, a linear range of 0.03-10.0 ng mL-1 for As(III), along with a detection limits of 0.0026 ng mL-1, and the relative standard deviations for As(III) and As(V) for 0.28-6.30%, were obtained. The proposed method was applied for the analysis of inorganic arsenic species in groundwater and lake water with the recovery of 98.00-102.0%.