The polluted water column is excited with the third harmonics(355 nm) of Nd∶YAG laser and fluorescence spectrum is detected by laser induced fluorescence technique. After analysed and processed the spectrum data,normalization of fluorescence intensity is obtained,which is the ratio of 450 nm value to 405 nm value. Commercial humic acid is diluted with different quantity of deionized water as water sample of known DOM concentration. The result has been shown that there is a good correlation between DOM concentration and the normalization fluorescence intensity of ultraviolet laser induced fluorescence. Therefore the LIF technique is a good method for the practical utilization of in vivo monitoring polluted water column.