Abstract: The fluorescence-enhancing agents YZ-Ⅰ and YZ-Ⅱ, which consist mainly of sodium pyrophosphate and polyphosphate respectively, for the laser fluorimetric determination of trace uranium are studied and the detection limit of uranium by using YZ-Ⅰ or YZ-Ⅱ in conjunction with the UA-3 uranium analyser reached 0.002 ppb. Linear corelation existed, extending through five orders of magnitude, with a precision of less than ± 5 % for a uranium content of more than 0.1 ppb. The uranium contents in aqueous solutions, including riverwater, lake water, groundwater, seawater etc. are determined by using YZ-Ⅰ or YZ-Ⅱ without separation of the foreign ions and pre-concentration of uranium.The TBP extraction-laser fluorimetric method for the determination of trace uranium is developed and reported. One determination lasted 3 minuets only. Among the 18 ions tested, 13 cations and anoins don't interfere the determination of uanium when their amounts is 107 times that of uranium. This method can therefore be used for samples containing a great quantity of interfering species.