A indoor constant temperature and humidity incubation experiment was conducted in which the dynamic changes of soil nitrogen forms during a 63 d incubation period was studied to explore the influences of the combined application of urea and slow-release urea plus 3,4-dimethylpyrazole phosphate (DMPP) on nitrogen transformation in lime concretion black soil. Seven treatments were designed, which included:1) CK (without fertilization), 2) N (only urea), 3) S (only slow-release urea), 4) NS (60% urea and 40% slow-release urea), 5) ND (urea plus DMPP), 6) SD (slow-release urea plus DMPP), and 7) NSD (60% urea and 40% slow-release urea plus DMPP). The results showed that:1) the content of ammonia nitrogen was significantly higher in ND than that in N during prior 35 d incubation period, which indicated that the addition of DMPP could effectively delay the process of ammonium oxidation. 2) Similarly, ammonia nitrogen content was higher in SD than that in S. Moreover, oxidation of ammonium was inhibited up to day 49 with reduced apparent nitrification rate, while the nitrification inhibition rate was enhanced. 3) Compared to NS, the content of ammonia nitrogen was significantly higher and the half-life of ammonia was extended up to 18.6 d in NSD. In addition, the nitrification inhibition rate in NSD increased significantly and the inhibition continued up to day 32. In conclusion, the ammonia oxidation processes were significantly inhibited and the residence time of ammonium in soil were significantly prolonged by the addition of DMPP in the treatment of urea combined application with slow-release urea, which exhibited a relative higher nitrification inhibition rate and a relative lower apparent nitrification rate. These findings provide scientific reference for application of urea and slow-release urea to prevent loss of nitrogen in farmland.