A method for the determination of antimony (Ⅲ) and antimony (Ⅴ) in geological samples (stream sediments) by hydride generation-atomic fluorescence spectrometry was developed in this paper.4.8 mol/L HCl could be used as the extractant with ultrasonic-assisted extraction. In the medium of 0.24 mol/L hydrochloric acid, antimony (Ⅲ) could be alternatively determined with 6 g/mL sodium citrate as the masking agent for Sb(V). Then antimony(Ⅴ) could be figured out by the subtraction method. The detection limit of the method was 0.075×10^-6 for Sb(Ⅲ) and 0.097×10^-6 for Sb(Ⅴ), and the relative standard deviation was 1.1% and 0.64% (n=11) for 40 ng/mL Sb(Ⅲ) and 40 ng/mL Sb (Ⅴ) standard solution. The proposed method was applied to the determination of antimony (Ⅲ) and antimony (Ⅴ) in geological samples, and a comparison between the extraction results and the aqua regia dissolution results shows that the extraction rate of antimony was higher than 80%, the recoveries were in the ranges of 83%～107% and 98%～114% for Sb(Ⅲ) and Sb(V),  respectively.