Abstract: A method for the determination of phosphorus (P) by molecular absorption of phosphorus monoxide (PO) using a high resolution continuum sourceatomic absorption spectrometer and an airacetylene flame has been developed. The factors affecting the determination such as instrumental conditions and parameters, spectral interferences and chemical interferences from coexistent elements and etc. were studied. The method has been applied to the determination of phosphorus in plant materials, such as leaves. Comparing with the other methods, this method provides the advantages of easy and simple of operation, more efficiency and is suitable for determination of phosphorus in plant samples.