A method is described for the determination of the Se in river water after precorncentration by stabilized temperature platform furnace and Zeeman background correction. A mixture of platinum and ascorbic acid was proved to be an adequte and powerful matrix modifier for the determination. Thermal pretreatment temperature of 1200°C can be used with the proposed modifier and concentration can be obtained directly via calibration curve without using the standard-addition technique. The method is sensitive, reliable and relatively simple, with the chracteristic mass, detection limit and recovery, 19.5pg/0.0044A.S., 1.55μg/L and 85.0-110.0%, respectively.