In order to address the serious soil acidification and compaction issues in aged tea gardens, four different fertilization treatments were implemented to analyze their effects on soil conditions and tea quality, aiming to identify the most effective soil improvement approach for severely acidified tea gardens. The results showed that applying a combination of organic and inorganic fertilizers, as well as biochar, could increase soil pH by 0.72 and 0.3 units, respectively. The combined application of organic and inorganic fertilizer had a significant effect on the content of nitrogen (N), phosphorus (P), and potassium (K) in the soil, as well as the microbial activity. Compared with the CK, the combined application of organic and inorganic fertilizers increased the content of tea extract of spring tea by1.5% and 3.05%, the content of tea polyphenols by 0.67% and 2.2%, and the content of theanine by 0.08% and 0.32% over two years. Sensory analysis showed that the combination of biochar and organic fertilizer had the most obvious effect on improving the tea quality in the aged tea garden, followed by the combination of organic and inorganic fertilizer. Therefore, for severely acidified aged tea gardens, the combined application of organic fertilizer and biochar, or biochar and organic fertilizer, can be recommended as effective soil improvement strategies.