[Objectives] This study was conducted te understand the process of soil nitrogen mineralization in Eucalyptus plantations, and te identify the characteso istics oS soii nitrogen mineralization with different litter inputs. [Methods] With the soil of the Eucalyptus plantation in Fusui County, Guangxi as the research object, the soit nitrooen mineralization of the Eucalyptus plantation under different litter ireatmeny (removing littee, adding litter and retaining litter) was studied by PVC tube closed-top in-situ incubation. [Resuls] 1 After 1 year of litter yeatment, the inoraanio nitrooen (NHQ-N + NO3 -N) in the soii ot different treat ment ranked as adding littee (20.15 mg/kg) > retaining littee (16.02 mg/kg) > removing littee (11.60 mg)/kg), and the dferences reached a sienificant levei (P < 0. 05). # Mter 30 d of in-situ incubation, there were sienificant dferences in soil nitrate nitrooen content before and after incubation in the three treatment (removing littee, adding littee, and retaining litter) before and after incubation (P<0.05), but no significant dferences were observed in soii ammonium nitrogen content (P >0. 05). Soii nitrate nitrogen contents increased from 1.47, 2. 01 and 1.72 mg/kg before incubation te 3.66, 6. 73 and 5. 02 mg/kg, respectively, and soil ammonium nitrogen content increased from 11.60,20.15 and 16. 02 mg/kg before incubation to 13. 65, 21.54 and 17.18 mg/kg, respectively. The net nitrogen mineralization quantities of the three treatments were 4.24, 6. 11 and 4.46 mg/kg, respectively, and the net nitrogen mineralization rates from larae te small were adding litter[0.180 mg/(kg * d) # > retaining litter[0.141 mg/(kg * d) # > removing litter[0.125 mg/(kg * d)$. Therefore, both removal and addition of inter affected the soil nitrogen input and nitrogen mineralization rate of the Eucalyptus plantation, thereby affecting soil nitrogen avnlabyity and the abnity of soii te mintain plant-ovailable nitrogen. [Conclusions] Thiz study provides a theoretici basis for nutrient management in Eucalyptus plantations, especially nitrogen nueetenemanagemene. [ABSTRACT FROM AUTHOR]