The ultraviolet absorption spectra of pyrazoles and 1-carboxamidepyrazoles were studied. The results indicated that substitution in the 3 or the 5 position it leads to a bathochromic shift of the position of the maximum absorption by about 3-4 nm, whereas in the 4 position leads to a much larger bathochromic shift (> 10 nm). The introduction of carboxamide causes a bathochromic shift of the position of the maximum absorption by about 20-26 nm. Its also leads to an increase in molar extinction coefficient by about 2-3 times. So UV methods were established for determining the contents of pyrazoles and their derivations. Using these methods, the content of 3,4-dimethylpyrazole phosphate (DMPP) in stabilized urea was determined to be 1.15% of urea-N, the hydrolytic half lives of 1-carboxamide-3-methylpyrazole (CMP) in water solution at 20, 25 and 30 degrees C were 48, 30 and 18 h, respectively, and the extraction percentage of nitrification inhibitor 3-methylpyrazole phosphate (MPP) in 3 soils by 3 different extractants were ranged from 63.2% to 89.2%.