Through a two-year field trial，we explored the effects of applying nitrification inhibitor (2-chloro-6- trichloromethylpyridine) at different periods on the yield and quality of mandarin orange and navel orange.8-year-old Nanfeng mandarin orange and 6-year-old Newell navel orange were used as test materials.Four treatments were set up:CK (without nitrification inhibitor)，BF+En (bud fertilizer with nitrification inhibitor)，SF+En (steady fruit fertilizer with nitrification inhibitor) and BF+SF+En (Both germination fertilizer and stable fruit fertilizer are combined with nitrification inhibitors)，and the effects of nitrification inhibitors amendment on yield，single fruit weight，quality，SPAD，physiological drop rate and number of spring and autumn shoots were analyzed.The results showed that compared with CK，the nitrification inhibitors amendment in different periods both had a tendency to increase the yield of mandarin orange and navel orange.SF+En and BF+SF+En significantly increased the mandarin orange yield by 17.1%，23.1%，respectively；BF+SF+En significantly increased navel orange yield by 19.7%.With the nitrification inhibitors amendment，it showed an upward trend of vitamin C content in mandarin orange，but a downward trend in the total acid content.Among them，SF+En and BF+SF+En vitamin C content increased significantly by 32.7% and 33.3%，and BF+En and SF+En total acid content decreased significantly by 14.5% and 12.7%，respectively.The content of vitamin C in navel orange significantly increased by 25.1% in SF+En，and there was no significant effect on total acid content，BF+SF+En significantly increased single fruit weight，peel thickness，horizontal and vertical diameters by 20.3%，14.9%，8.5% and 7.6%，respectively.BF+SF+En significantly increased the number of spring and autumn shoots of mandarin orange and navel orange，of which the number of spring shoots of BF+SF+En increased significantly by 32.9% and 42.4%，respectively，while the number of autumn shoots increased by 15.1%，24.9%.In summary，both the bud fertilizer and the stable fruit fertilizer combined with nitrification inhibitors have the best effect on increasing the growth and yield of mandarin orange and navel orange，Among them，the vitamin C content of mandarin orange has increased significantly，and the single fruit weight，peel thickness，horizontal and vertical diameters of navel orange are significantly increased.