Abstract: A method for the determination of fluorine in marine carbonate rocks by ion selective electrode with pyrohydrolysis sample pretreatment has been developed. The detection limit of the method is 25.1 μg/g for fluorine and the recovery is 83.80%～107.90% with precision of 5.28%RSD (n=11). The method has been applied to the determination of fluorine in marine carbonate rock samples with satisfactory results and provides the advantages of high efficiency and simple operation.