Abstract: Robusta coffee was characterized by insufficient flavor complexity and prominent bitter and astringent notes, Therefore, the flavor quality of coffee green beans could be effectively improved via targeted regulation of their flavor precursor contents. Hainan grown Robusta green coffee beans were employed as the experimental material to investigate the effects of ultrasound-assisted fructose soak (UFS) with different durations on the flavor precursor compounds, water-soluble components, green bean structure, and sensory quality. Specifically, fructose-soaked samples served as the control group, whereas untreated samples were designated as the blank group. The results indicate that the total sugar content in both FS and UFS coffee samples was significantly higher than that in UNT (P<0.05). When the total soaking duration was 2.5 h, the total sugar content of the sample subjected to 15 min of ultrasonic-assisted fructose soaking (UFS15) reached 54.65 mg/g, which was 2.45 times higher than that of UNT and 1.33 times higher than that of FS. This finding suggests that 15 min of ultrasonic treatment enhances the penetration of fructose solution into coffee green beans. Scanning electron microscopy (SEM) results revealed that ultrasound treatment damaged the surface structure of coffee green beans; When the treatment duration exceeded 15 min, honeycomb-like pores appeared on the bean surface, and these pores gradually enlarged with prolonged treatment. Additionally, UFS significantly reduced the fat content of coffee green beans (P<0.05), while the samples treated with 5 min of ultrasonic-assisted fructose soaking (UFS5) exhibited the highest contents of protein, total polyphenols, and total flavonoids. Furthermore, after 20 min of ultrasonic-assisted fructose soak (UFS20), the total amino acid content in coffee green beans was the highest, reaching 50.99 mg/g. ¹H nuclear magnetic resonance (¹H NMR) analysis demonstrated that the contents of fructose, lactic acid, and chlorogenic acid in UFS5 are 171%, 38%, and 17.39% higher than those in UNT, respectively; whereas these contents are 1.3%, 15.6%, and 6.7% higher than those in FS. Sensory evaluation results indicated that UFS5 samples achieved the highest sensory score (74.92 points), with superior performance particularly in dry and wet aroma, sour-salty balance, mouthfeel, and aftertaste. Additionally, coffee green beans treated with FS and UFS exhibited a significantly darker coloration relative to untreated samples. This study provides a theoretical basis for improving the flavor profiles and overall quality of Robusta coffee, and contributes to the enhancement of premium-grade quality for Hainan-sourced coffee products.