Abstract: A method was proposed for the determination of trace iron released from sulfides in geological samples. Iron was extracted and spectrophotometry measured by sulphosalicylic acid after sulfides were oxidized by sodium hypochlorite. The results show that 30% of sodium hypochlorite soaking the sample for more than 40 hours could transform iron sulfides completely into colloidal ferric hydroxide, which can be easily extracted by the sulphosalicylic acid solution. We integrate the selective sepatation,enrichment and determination of iron in the procedure to make the method simple and suitable for determination of iron sulfides in geological samples.