China is currently the largest sweet potato producer globally. The postharvest starch and soluble sugar (glucose, fructose, and sucrose) contents in storage roots not only influence sweet potato utilization and commercial value (including taste, nutritional quality, and food processing properties), but also affect sprouting, weight loss, and decay during storage and transportation. Studies on tubers/roots such as potato and carrot have demonstrated that vacuolar invertase (VIN) serves as the primary sucrose-cleaving enzyme determining postharvest sugar composition and content. However, the key sucrose-cleaving enzyme regulating postharvest sugar metabolism in sweet potato storage roots remains unclear. This study systematically investigated sugar metabolism characteristics in storage roots of ‘Kokei 14’, a major sweet potato cultivar in Hainan Province, under room temperature storage (25 ℃) and low-temperature storage (15 ℃), aiming to identify the principal sucrose-cleaving enzymes affecting postharvest sugar composition and content. Low-temperature storage enhanced preservation quality by reducing dry matter loss and sprouting rate through suppression of hexokinase (HK) activity and respiratory intensity. Compared with room temperature storage, low-temperature treatment induced greater increases in soluble sugar (glucose, fructose, and sucrose) content and more pronounced starch degradation, accompanied by significantly higher β-amylase activity, indicating that low-temperature storage promotes starch hydrolysis into soluble sugars. During room temperature storage, cell wall invertase (CWIN) and sucrose synthase (Sus) activities generally declined, while VIN activity initially increased before returning to baseline levels. Notably, cytoplasmic invertase (CIN) activity exhibited a continuous upward trend, suggesting CIN as the key sucrose-cleaving enzyme responsible for hexose accumulation under ambient conditions. Conversely, low-temperature storage induced continuous declines in all three invertase activities but progressively increased Sus activity, indicating Sus as the predominant enzyme mediating hexose accumulation under cold storage. Transcriptional analysis identified IbCIN4 as the key gene family members regulating CIN activity elevation at room temperature, while IbSus6 was determined as the primary regulator of Sus activity enhancement under low-temperature conditions. This study reveals that different postharvest storage temperature induces shifts in the predominant sucrose-cleaving enzymes governing hexose accumulation in sweetpotato storage roots. Notably, our findings contrast with previous reports on potato tubers under cold storage, demonstrating that Sus rather than VIN serves as the key enzyme regulating hexose content in sweetpotato roots under low-temperature conditions. The results would establish a theoretical foundation for future genetic engineering approaches to improve postharvest quality of sweetpotato storage roots.