The influence of nitrification inhibitor(NI) 3,4-dimethylpyrazole phosphate (DMPP) on nitrate accumulation in greengrocery( Brassica campestris L. ssp. chinensis) and vegetable soil at surface layer were investigated in field experiments in 2002 and 2003.Results showed that NI DMPP took no significant effect on yields of edible parts of greengrocery, but it could significantly decrease NO3- -N concentration in greengrccery and in vegetable soil at surface layer. In addition, NI DMPP could reduce the NO3--N concentration during the prophase stage of storage.