Abstract: For analyzing the speciation of inorganic arsenic (As) in water sampled from Fujian tobacco growing area, an ICP-MS method was developed,N-(2-aminoethyl)-3-aminopropyl trimethoxysilane (AAPTS) modified silica-coated magnetic nanoparticles were served as adsorbent for solid phase extraction, and the main factors influencing As extraction efficiency were investigated. The results showed that:1) The optimized extraction conditions were:sample volume 150 mL, pH value 6.0, AAPTS modified silica-coated magnetic nanoparticles 50 mg, 1.0 mol/L HNO₃ 0.5 mL, and desorption time 2 minutes. 2) The magnetic material selectively adsorbed As(V) in the sample solution, while As(III) was not adsorbed. The limit of detection for As (V) was 0.2 ng/L with the intra-day relative standard deviation (C_As(V)=10 ng/L,n=7) of 6.8%; the concentration of As(III) in water samples could be calculated by subtracting As(V) from the total As. 3) The method was validated by determining the content of As(III, V) in standard water sampleGBW(E)080231. The detection value was (48.3±1.31) ng/mL and basically consistent with the standard value of (51.0±2.63) ng/mL. 4) Water samples from Sanming, Longyan and Nanping tobacco growing areas contained lower inorganic As, mainly As (V). This method is simple, fast, sensitive, accurate and suitable for the speciation analysis of inorganic As in batches of water samples from tobacco growing areas.