A method for determination of trace Cr(III) in natural water and drinking water by GFAAS after separation by coprecipitation-floatation with Al(OH)3 has been studied. Cr(VI) was determined also after being reduced by FeSO4. Conditions of Cr(III) floatation such as pH, the amount of floatation agent and coprecipitator-Aluminium added, the flow rate of nitrogen gas, the floatation time etc. were discussed. The influence of coexisting elements was investigated. The detection limit is 0.027 microg/L (n = 15). For Cr(III) concentration level of 0.5 microg/L, the RSD is 3.4% and the recovery of Cr(III) is 96.0-104.0%.