Abstract: A method for the remote determination of ultra-low level uranium using laser-induced optical fiber fluorimetry is reported. The structure of the optrode which effects the fluorescence measurement of uranium is studied. Results show that higher detection efficiency and ratio of signal to noise can be obtained when the angle between the incident and exit optical fibers of the optrode is 25 degrees and the thickness of the sample determined is over 40 mm. The detection limit of uranium in 1mol/1 H3PO4 is 0.4 ppb and the precision is better than±10%.