In this paper the spectrophotometric method for determination of trace amount of uranium in weak acidic medium by chlorophosphonazo-mA is described. The composition of the complex was estimated to be 1:1 by slope ratio method. The apparent molar absorption of uranium at 690 nm is 1×10

5

. Beer's law is obeyed for 0—12.0 µg of uranium in 10ml solution. The coefficient of variation for uranium is 0.75%. The method has been applied to the determination of trace amounts of uranium in the extraction process of uranium

and the determination of

233

U from neutron irradiated ThO

2

.