To explore the regulatory effects of brackish water irrigation concentrations on plant growth and fruit quality of tomato in the arid regions of Northwest China, a pot experiment was conducted using the cherry tomato cultivar ‘Xiangfei No.3’ as the test material. Four NaCl brackish water irrigation gradients were set: 0 g/L (CK), 1 g/L (T₁), 2 g/L (T₂), and 3 g/L (T₃). We systematically analyzed the impacts of different treatments on tomato growth indicators (including plant height and stem diameter) and fruit quality indicators (such as soluble sugar, lycopene, organic acids, and sugar-acid ratio), followed by a comprehensive evaluation via principal component analysis (PCA). The results showed that moderate brackish water irrigation significantly promoted tomato growth; the plant heights of T₁, T₂, and T₃ treatments were all higher than that of CK at the mature stage. The T₁ treatment exhibited the most significant promotion effect on soluble sugar accumulation, with the soluble sugar contents in the 1^st to 5^th ear fruits at the mature stage increased by 38.24%, 30.56%, 26.47%, 34.29%, and 24.14% respectively compared with CK. The T₂ treatment significantly increased the lycopene content, where the lycopene contents in the 1^st to 5^th ear fruits at the mature stage were significantly higher than those of CK (P<0.05), with an increase range of 20.29%-29.31%. The T₃ treatment achieved the highest sugar-acid ratio, which significantly optimized the flavor quality of fruits. At the green mature stage, the T₁ treatment facilitated the accumulation of organic acids; the contents of malic acid, citric acid, tartaric acid, lactic acid, and oxalic acid in the first four ear fruits were all higher than those of CK, and the organic acid contents in the 1^st, 2^nd, and 4^th ear fruits ranked the highest among all treatments. The PCA evaluation indicated that fruit quality indicators under high-concentration brackish water irrigation ranked higher at the green mature stage, while those under suitable-concentration brackish water irrigation (T₁-T₂) performed best at the color turning and mature stages. This study clarified the optimal brackish water irrigation concentrations for different quality indicators, providing a theoretical basis and technical scheme for the safe application of brackish water irrigation in cherry tomato production in freshwater-scarce areas of Northwest China.