Abstract: It is the citrus predominance district programming of Southern Jiangxi promulgated recently by Ministry of Agriculture. The citrus area is about 100000 ha in this region, and most of the orchards are on hilly and mountainous land where purplish red sandstone of Tertiary period is extensively distributed. The research had been carried out through field experiment since 2006, and mainly studied the effect of boron fertilizer on the yellow leaves and fallen fruit of Newhall Navel Orange（Citrus sinensis Osbeck Newhall）in Southern Jiangxi. Which installed two B levels (CK, 0 mg/kg and +B, Na2B4O7.10H2O 15 g/plant), each level had three repetitions. The result showed that boron applying was obvious improvement the growth of the navel orange and boron nourishment condition, the number of fruit per plant average increase 39.8% compared no boron fertilizer, and the number of old yellow leaves reduced from 12.9% to 3.2 %; Weight and number of fruit both increased, the weight of single fruit increase 11.9%, and the fruit yield of per plant increase 10.5 %. Totally, the fruit yield will increase about 23.3% per hectare, which can bring high economic profit to fruit grower，there will be need 90% boron for orange growing at fruit expanding stage. Boron content and accumulation of each fruit organ significantly increased, and boron distribution also more proper in plant different organ. Therefore, boron applying could allay leaves etiolation and fruit fallen of Newhall Navel Orange, so increase fruit yield.