[Objective] To investigate the effects of biochar combined with nitrification/urease inhibitors and straw mulching on nitrogen and phosphorus leaching under in situ field conditions，aiming to provide scientific evidence for controlling nitrogen and phosphorus leaching in tea plantations. [Methods] A red soil hillslope tea plantation in the subtropical region was selected as the study area. Five treatments were established：no fertilization（CK）， conventional fertilization（CON），biochar addition（BC），biochar combined with nitrification/urease inhibitors （BNI），and straw mulching（RS）. Over a one-year observation period，changes in soil physicochemical properties and leaching losses of nitrogen and phosphorus under natural rainfall conditions were monitored. [Results] During the observation period，compared to the CON treatment，the BNI treatment exhibited the highest soil ammonium nitrogen and nitrate nitrogen mass fractions，which were 2.8% and 72.8% higher，respectively. The higher ammonium nitrogen and nitrate nitrogen levels in the BNI treatment led to an increase of total nitrogen concentration in the leaching solution. Soil nitrogen and phosphorus leaching primarily occurred during the rainy spring and summer seasons. The BC treatment showed the highest leaching coefficient at 24.3%，while the RS treatment had the lowest at 8.3%. For total nitrogen loss in leaching solution，the BNI treatment（275.0 kg/hm²） was highest，and the RS treatment（65.9 kg/hm²） was the lowest. For total phosphorus loss，particulate phosphorus was the dominant form of loss，with the BC treatment yielding the highest loss（201.5 g/hm²）and the RS treatment the lowest（32.4 g/hm²）. Compared with the CON treatment，the RS treatment reduced total nitrogen loss in leaching solution by 43.6%，while the BNI and RS treatments decreased total phosphorus loss by 39.1% and 77.2%，respectively. [Conclusion] Considering both soil plant-available nutrient content and the effectiveness in controlling nitrogen and phosphorus leaching，straw mulching is an effective management practice for reducing nitrogen and phosphorus losses in tea plantations.