To establish a spectrophotometric method for detecting selenium in drinking water,some subjects,such as the features of absorption spectrum of the reacting product of selenium and diaminonaphthalene,disturbance of other coexisting ions,detection range,detection limit,precision and accuracy were studied.The results showed that:the maximum absorption wavelength of the reacting product of Se4+and 2,3-diaminonaphthalene was 377 nm,the detection limit,molar absorptivity (ε377) and linear range of this method was 0.018 μg/50 ml,2.7×104 L/(mol·cm)and 0.2～10 μg/50ml respectively.The regressive equation was A＝0.077C＋0.014 with a correlation coefficient r value of 0.9999.The relative standard deviation (RSD) and recovery rate were ＜54.7% and 96.5%～106% respectively.This method was simple,sensitive and accurate,could meet the requirement of the routine monitoring of selenium in drinking water.