To provide scientific basis for management and efficient utilization of nitrogen in fields, effects of combined application of organic and inorganic fertilizers plus DMPP (3,4-dimethypyrazole phosphate) on nitrogen transformation in soils as affected by to various factors were studied. For that end, an aerobic thermostat pot experiment was designed to have various affecting factors, like fertilization rate, soil moisture, environmental temperature, soil type, etc., and carried out. After 60 days of incubation, it was found that NH₄⁺-N concentration was 89 times higher and NO₃^--N concentration 57.8% lower in the pots higher in fertilization rate than in the pots conventional in fertilization rate (no DMPP was added in either pots); in the pots subjected to flooding and combined application of organic and inorganic fertilizers plus DMPP, NH₄⁺-N concentration kept on rising and nitrification process was more significantly inhibited; NH₄⁺-N concentration was 56 times higher and NO₃^--N concentration 18 times lower in the pots incubated under 15℃ than in the pots under 25℃, and NH₄⁺-N concentration was 30 and 31 times higher and NO₃^--N concentration was 44.3% and 66.4% lower in the pots of red soil than in the pots of silt paddy soil and blue clayey paddy soil, respectively. The optimal nitrification inhibitory effect was observed during the period from day 30 to day 40 in the pots of blue clayey paddy soil, silt paddy soil and red soil subjected to combined application of organic and inorganic fertilizers plus DMPP under 25℃, and inhibitory effect of the treatment may last throughout the experiment period of 60 days. Obviously the addition of DMPP could increase NH₄⁺-N concentration in the pots subjected to combined application of organic and inorganic fertilizers, and effectively extend residence of the NH₄⁺-N in the soils, and keep NO₃^--N concentration at a lower level for a longer period. The inhibitory effect of DMPP was more outstanding in the pots subjected to high rates of combined fertilization. Low temperature is benefit to the inhibitory effect of DMPP. It is, therefore, worthwhile to do some further studies on mechanisms of different factors affecting effects of combined application of organic and inorganic fertilizers plus DMPP on nitrogen transformation.