The phenomenon of soil magnesium(Mg)deficiency is common in the Jinggang pomelo planting area in Jiangxi province.To investigate the effect of two ways of Mg fertilizer application by soil application and foliar spraying on yield and quality improvement of the Jinggang pomelo，the Jinlan Pomelo(Citrus maxima cv.Jinlan Yu) and Jinsha Pomelo(Citrus maxima cv.Jinsha Yu) of Jinggang pomelo were used as research subjects.A field experiment was conducted from December 2021 to November 2022 in Xingqiao and Baishui town，Jiangxi province，with three treatments:control(CK)，soil-applied Mg fertilizer(Mg-S)，and foliar sprayed Mg fertilizer(Mg-L)，to investigate the effects of soil application and foliar sprayed Mg fertilizers on the nutrient content of Jinggang pomelo leaves，photosynthesis rate(Pn)，SPAD value，grapefruit yield and fruit quality.The results showed that soil application and foliar spraying of Mg fertilizer significantly increased the Mg content of Jinggang pomelo leaves in the ranges of 3.6%-7.3% and 9.5%-12.4%，respectively.It increased the nitrogen content of leaves，and for Mg-S and Mg-L treatments in the Xingqiao experiment were significantly，the it was increased by 17.5% and 19.7%，respectively，compared with the CK.Mg fertilization significantly increased Pn of Jinggang pomelo leaves by 14.2%-23.5% and 32.4%-34.3%，respectively，in Mg-S and Mg-L treatments. The Mg-L treatment significantly increased the SPAD value of leaves by 10.2%-14.6%，while the Mg-S treatment had less effect on the SPAD value. Compared with the two Mg application methods，foliar application of Mg was more effective in enhancing leaf nitrogen and Mg contents as well as Pn and SPAD value. Mg fertilizer application increased the yield of Jinggang pomelo and improved its fruit quality. Compared with CK，single fruit weight enhancement of Mg-S and Mg-L treatments ranged from 1.25% to 5.90% and 3.47% to 7.64%，respectively；in the Baishui，the soluble solids，total sugars，and solid-acid ratio of Mg-S fruits were significantly increased by 12.1%，10.6%，and 37.7%，respectively，compared with those of CK；and those of the Mg-L treatments were significantly increased by 13.6%，12.3%，and 27.6%，respectively. The comprehensive evaluation of fruit quality using factor analysis showed that the comprehensive score of the Mg-L treatment was higher than that of the Mg-S and CK treatments，indicating that foliar application of Mg had a better effect on the quality enhancement of pomelo. In conclusion，the two methods of Mg application were both conducive to improving the nutrient Mg and nitrogen content of Jinggang pomelo leaves，enhancing the SPAD value of leaves，and enhancing the Pn of leaves；thus，increasing the indexes of Jinggang pomelo’s single fruit weight，soluble solids and solid-acid ratio，and realizing a synergistic enhancement of yield and quality，and the effect of foliar application of Mg was better than that of soil application.