The Three Gorges Reservoir area is a crucial region for sweet orange cultivation in China.However，the issue of fruit cracking(internal cracking)severely affects fruit quality and farmers’ economic returns.Investigating the causes of peel cracking and proposing preventive measures are vital for improving the quality and efficiency of the citrus industry.This study used 13-year-old Tarocco blood orange trees on Citrange Rootstocks in Wanzhou，Chongqing.Three treatments were set up:spraying with clean water as a control(CK)，spraying with 0.2% borax(Na2B4O7)and spraying with 0.2% boric acid(H3BO3).The effects of boron application on the fruit skin hardness，thickness，mineral elements and internal cracking of Tarocco blood orange were analyzed.The results showed that both boron fertilizer treatments significantly increased the fruit skin thickness and hardness of Tarocco blood oranges，compared to the CK.Boron application increased the contents of boron，calcium and potassium in the peel，with the increased boron content enhancing crack resistance，and the increased calcium and potassium contents helping to maintain stable structure and water balance of the fruit.Additionally，it effectively reduced the occurrence of sponge layer cavities in the peel and alleviated internal cracking.Under the experimental conditions，boron application increased the contents of boron，calcium and potassium in the fruit peel of Tarocco blood oranges in the Chongqing Three Gorges reservoir area.This led to increased fruit skin thickness and fruit hardness，reduced crack sizes and voids in the sponge layer of the fruit peel，and decreased incidence of internal cracking.The overall effect of the Na2B4O7 treatment was relatively better.