Existing studies on the wind-induced vibration response of large-span flexible photovoltaic supports mostly focus on local measurement points and ignore the spatial variability of structural aeroelastic responses. Most researches also concentrate on the wind vibration coefficient of vertical displacement, without considering the effect of three-dimensional displacement on the overall wind vibration coefficient. To systematically investigate the refined wind-induced vibration characteristics of large-span flexible photovoltaic support arrays, this paper conducts aeroelastic vibration measurement wind tunnel tests on a 42 m-span flexible photovoltaic support array with five rows and three spans. The full-field three-dimensional displacement responses of the structure are acquired by adopting the three-dimensional digital image correlation (3D-DIC) method. Wind directions of 0°, 45° and 180° are identified as the most unfavorable wind angles. The evolution laws of wind-induced vibration responses between spans and rows under various wind directions and wind speeds are analyzed, and the key regions and displacement characteristics of wind vibration responses corresponding to each most unfavorable wind direction are clarified. The results reveal that the dominant response of the large-span flexible photovoltaic support array differs obviously under different wind directions. The structural response is dominated by vertical displacement at 0° wind direction, jointly controlled by vertical and horizontal displacements at 45° wind direction, and dominated by vertical displacement accompanied by prominent horizontal displacement at 180° wind direction. Based on the test data, the entropy weight method is used to objectively quantify the contribution weights of vertical and horizontal displacements to structural wind-induced vibration responses. An equivalent model of wind vibration coefficient is established considering the coupling effect of bidirectional displacements. The accuracy and reliability of the model are verified through comparison with the displacement amplitude weighting method and spatial vector superposition method. The most unfavorable equivalent wind vibration coefficients under respective working conditions are 1.53 for Row R5 at 0°, 1.52 for Row R1 at 45°, and 1.63 for Row R1 at 180°. The conclusions of this study can provide references for the wind-resistant design and wind vibration coefficient selection of large-span flexible photovoltaic support array structures.