Abstract: 【Objective】To determine the optimal dark adaptation duration and measurement light intensity for assessing chlorophyll fluorescence parameters in grape leaves，and to analyze the diurnal variation characteristicss of these parameters. This study aimed to provide recommendations for optimizing measurement protocols，thereby offering theoretical reference for further research into grape photosynthetic characteristics and enhancing the accuracy and reliability of experimental data.【Method】Healthy，mature leaves of Shine Muscat and Kyoho grape varieties aged 40-50 d were selected. The JIP-test and principal component analysis（PCA）were utilized to investigate the rapid chlorophyll fluorescence induction kinetics（OJIP）curves under different dark adaptation durations（5，10，15，20，25，30，35 and 40 min），various measurement light intensities［500，1000，1500，2000，2500，3000 and 3500 μmol/ （m²·s）］，and at different times throughout the day（8：00，10：00，12：00，14：00，16：00，18：00 and 20：00）. The influence of these experimental conditions on the chlorophyll fluorescence parameters was evaluated.【Result】Dark adaptation duration and measurement light intensity greatly influenced the chlorophyll fluorescence parameters of grape leaves. Extended dark adaptation durations and increased measurement light intensities resulted in more stable and reliable fluorescence parameter measurements. OJIP curve characteristics indicated that under short dark adaptations（5-15 min），the characteristic interval（OJ phase，JI phase and IP phase）relatively variable fluorescence difference（ΔW_OJ、ΔW_JI和ΔW_IP）curves between each dark adaptation duration and dark adaptation 5 min had a large variation，parameters such as initial fluorescence（F_o），maximum fluorescence（F_m）and maximum photochemical efficiency（F_v/F_m）fluctuated greatly. When dark adaptation exceeded 30 min，the parameters had no significant difference（P>0.05，the same below），and tended to be stablized. With increasing measurement light intensity，F_m，F_v/F_m the initial slope of OJIP curves（M_o），and number of reaction centers per unit area （RC/CS_m）showed an upward trend，and the ΔW_OJ、ΔW_JI和ΔW_IP curves between each measured light intensity and the measured light intensity at 500 μmol/（m²·s）showed positive K peaks，negative H peaks and positive G peaks. Once the light intensity exceeded 3000 μmol/ （m²·s），no further significant changes in fluorescence parameters were observed. Most chlorophyll fluorescence parameters of grape leaves changed with diurnal variations of times，with higher photosystem II（PSII）photochemical efficiency before 12：00，a decline at 14：00，and a gradual recovery of PSII to optimal levels after 16：00.【Conclusion】For accurate OJIP curve measurements of grape leaves，a dark adaptation duration of at least 30 min and a minimum measurement light intensity of 3000 μmol/ （m²·s）are recommended. Optimal measurement times are before 12：00 and after 16：00 to ensure the accuracy and reliability of the results.