‘Nanfeng tangerine’ was used as the experimental material in this study. The fruits sprayed with 0.14 g/L chelating calcium on the fruit surface before high temperature coming (June) as calcium treatment, and the fruits sprayed with water were the control. The calcium signal transduction and antioxidant enzyme gene expression levels, antioxidant enzyme activities and reactive oxygen species (ROS) contents were determined. In addition, the gene expression characteristics of antioxidant enzymes regulated by the genes of calcium signal transduction pathway in ‘Nanfeng tangerine’ peels during the sunburn occurrence period with calcium treatment were analyzed to reveal the molecular and physiological mechanism of calcium alleviating the tangerine sunburn disease, and to provide a theoretical basis for preventing and reducing sunburn physiological disease of tangerine in the fruit production by spraying chelating calcium. The results showed that: (1) the incidence of sunburn in ‘Nanfeng tangerine’ fruits treated with calcium was significantly lower than that of the control, which decreased by 13.76%. (2) The results of real-time fluorescence quantitative PCR revealed that the expressions of calcium signaling pathway-related genes CsNADK, CsMPK8, CsCPK, CsRBOH, CsCAMK1 and CsGAD, and antioxidant genes CsSOD, CsCAT, CsPOD, CsAPX, CsGSR and CsGPX in the ‘Nanfeng tangerine’ peels were significantly up-regulated by calcium treatment. (3) The activities of antioxidant enzymes SOD, CAT, POD, APX, GR and GPX were significantly increased, and the contents of ₂^-·, H₂O₂ and MDA were significantly reduced in ‘Nanfeng tangerine’ peels by calcium treatment. (4) Fluorescence staining results revealed that the peel cells produced excessive green fluorescence of ROS, and the fluorescence accumulated diffusely with the duration of stress, while the ROS fluorescence intensity was significantly weaker in all calcium treatments than that in the control during the period of high temperature and intense direct light stress from July to October. These results indicated that the up-regulated expressions of calcium signaling pathway-related genes regulated the antioxidant gene expression and the enzyme activities, scavenging excess ROS and maintaining the balance of ROS metabolism in the tangerine peels, thus improving the anti-sunburn ability of the tangerine peels. A simple and effective technical measure to prevent sunburn in tangerine production is to spray chelating calcium on the fruit surface before the high temperatures coming.