The study investigated the effects of four potassium-containing fertilizers (complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate) on sugar and organic acid metabolism in grape fruits. The results showed that all four fertilizers increased the activity of enzymes involved in sugar and organic acid metabolism at all stages of grape fruit development. During the later stages of fruit development, potassium-containing fertilizers increased the total soluble solid content and sugar content while decreasing the titratable acid content and organic acid content. At the ripening stage, complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate increased the total soluble solid content by 1.5, 1.2, 3.5, and 3.4 percentage points, respectively, and decreased the titratable acid content by 0.09, 0.06, 0.18, and 0.17 percentage points, respectively. Transcriptome analysis revealed that potassium-containing fertilizers enriched genes involved in fruit quality, including carbon metabolism, carbon fixation in photosynthetic organisms, glycolysis and gluconeogenesis, and fructose and mannose metabolism. Potassium-containing fertilizers also affected the expression levels of genes regulating sugar metabolism and potassium ion uptake and transport. Overall, potassium-containing fertilizers promoted sugar accumulation and reduced acid accumulation in grape fruits, with potassium sulfate and potassium dihydrogen phosphate showing the best effects. The study also found that potassium-containing fertilizers increased the total potassium content in grape fruits. The results suggest that potassium sulfate and potassium dihydrogen phosphate are suitable potassium fertilizers for grape production to improve fruit quality.The study investigated the effects of four potassium-containing fertilizers (complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate) on sugar and organic acid metabolism in grape fruits. The results showed that all four fertilizers increased the activity of enzymes involved in sugar and organic acid metabolism at all stages of grape fruit development. During the later stages of fruit development, potassium-containing fertilizers increased the total soluble solid content and sugar content while decreasing the titratable acid content and organic acid content. At the ripening stage, complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate increased the total soluble solid content by 1.5, 1.2, 3.5, and 3.4 percentage points, respectively, and decreased the titratable acid content by 0.09, 0.06, 0.18, and 0.17 percentage points, respectively. Transcriptome analysis revealed that potassium-containing fertilizers enriched genes involved in fruit quality, including carbon metabolism, carbon fixation in photosynthetic organisms, glycolysis and gluconeogenesis, and fructose and mannose metabolism. Potassium-containing fertilizers also affected the expression levels of genes regulating sugar metabolism and potassium ion uptake and transport. Overall, potassium-containing fertilizers promoted sugar accumulation and reduced acid accumulation in grape fruits, with potassium sulfate and potassium dihydrogen phosphate showing the best effects. The study also found that potassium-containing fertilizers increased the total potassium content in grape fruits. The results suggest that potassium sulfate and potassium dihydrogen phosphate are suitable potassium fertilizers for grape production to improve fruit quality.