‘Ehime Kashi No. 28’ （Citrus unshiu × C. sinensis） was used to study the effects and potential mechanisms of fruit thinning through shortening pruning of bearing shoots on fruit quality to clarify the value of fruit thinning through shortening pruning of bearing shoots at the stage of full bloom in the simplified cultivation of citrus.The results showed that fruit thinning through shortening pruning significantly improved the efficiency of thinning compared with manual single-fruit thinning.The single fruit weight，transverse diameter，and longitudinal diameter of the fruit from the thinning through shortening pruning-treated ‘Ehime Kashi No. 28’ was significantly higher than that from the control group （CK） at 150 and 165 days after flowering blooming （DAFB）.The content of soluble solids in the fruit from thinning through shortening pruning-treated group was slightly increased at several stages at 165，180 and 195 DAFB，while the content of titratable acid was significantly reduced，leading to a marked improvement in the sugar-acid ratio at 135，165，180 and 195 DAFB compared with that in CK （P<0.05）.The results of correlation analysis showed that there was extremely and significantly positive correlation between the sugar-acid ratio and the equatorial diameter in the fruit with equatorial and longitudinal diameters ranging from 37 to 68 mm.The results of quantitative real-time PCR analysis showed that the expression level of CiSS1 and CiSPS1，two genes involved in the synthesis of sugar，was significantly increased in the fruit from the of treatment thinning through shortening pruning at 165 and 195 DAFB compared with that in CK.The expression level of CiPEPC1 gene involved in the metabolism of organic acid was significantly decreased at 135，165 and 195 DAFB，while the expression level of CiNADP-IDH1，CiAco1，and CiACLα1，genes involved in the degradation of citric acid，was significantly upregulated at 135，165 and 195 DAFB.It is indicated that fruit thinning through shortening pruning of bearing shoots increases the content of sugar and decreases the content of acid by changing the expression of genes involved in the metabolism of sugar and acid.In summary，fruit thinning through shortening pruning of bearing shoots at the stage of full bloom has a significant effect on improving the efficiency of fruit thinning and the fruit quality.It will provide theoretical support for its extension as a simplified，labor-saving cultivation technique for producing citrus fruits with high quality and large size.