Abstract: Objective: Previously, our group screened a strain of Lactobacillus casei YZU01 that could efficiently remove patulin from apple juice. This article aimed to study the effect of L. casei YZU01 on the quality of apple juice during the removal of patulin from apple juice. Methods: The quality parameters of apple juice, including organic acids (citric acid, tartaric acid, fumaric acid, acetic acid and L-malic acid) and sugar content (glucose and galactose), acidity, non-enzymatic browning index, light transmittance, and color parameter, were assessed in three groups: commercial apple juice (CAJ), apple juice supplemented with patulin (CAJ-Patulin), and apple juice supplemented with patulin after degradation by L. casei YZU01 (CAJ-Patulin-L. casei YZU01). This analysis was conducted using high performance liquid chromatography (HPLC), pH meter, UV spectrophotometer, and colorimeter. Results: The content of citric acid, tartaric acid, fumaric acid and acetic acid in the group of CAJ-Patulin-L. casei YZU01 was increased from 0.18, 2.3, 0.12, and 0.00 g/kg to 2.11, 3.4, 0.15, and 0.66 g/kg, respectively. However, the content of L-malic acid, glucose and galactose in the group of CAJ-Patulin-L. casei YZU01 was decreased from 7.31, 38.59, and 67.55 g/kg to 5.26, 1.59 and 28.37 g/kg, respectively. The change of sugar and acid contents in the group of CAJ-Patulin-L. casei YZU01 had little effect on the acidity of apple juice. Furthermore, L. casei YZU01 treatment would not cause non-enzymatic browning reaction and had not adverse effects on the color of apple juice, but it would cause a fluctuation in light transmittance. In addition, after 72 hours of degradation, L. casei YZU01 had little effect on the L^* and b^* value of apple juice, but slightly increased the a^* value, which represented that the green color of apple juice became lighter. In conclusion, the sugar and acid contents of apple juice were changed after treatment with L. casei YZU01, but no non-enzymatic browning reaction and color change was observed.