Abstract: 【Objective】 To discuss physiological regularities of Siraitia grosvenorii mogroside Ⅴ biosynthesis. 【Method】 Comparative experiments of variety, shading, gas storing and low-temperature storing were carried out. Through these experiments, correlations between Siraitia grosvenorii mogrosides and saccharides metabolizing in fruits, effects of photosynthesis, respiration and temperature on them were analysed. 【Result and conclusion】 In 30 d fruits, mogrosides were mainly mogroside ⅡE and Ⅲ, sucrose and glucose content were low. During 30-70 d, mogroside ⅡE and Ⅲ content rapidly decreased; sucrose and glucose content increased; mogroside Ⅴ occrred, and its content sharply rose to near the peak value. During 70-90 d, mogroside Ⅴ was what only detected and found among mogrosides; sucrose content continually increased; glucose content obviously decreased. The higher photosynthetic rates of the variety, the higher its mogroside Ⅴ and glucose content. In shading conditions, photosynthetic rate of leaves decreased, but mogroside Ⅴ and glucose content of fruits both climbed up. Both gas storing and low-temperature storing improved glucose accumulation but inhibited mogroside Ⅴbiosynthesis. These studies suggested that low saccharide group mogrosides gradually combined glucoses into mogroside Ⅴ. It did not improve mogroside Ⅴ biosynthesis that leaf photosynthesis and fruit respiration were regulated to increase glucose amount at a late developmental stage. These results showed that low saccharide group mogrosides amount and key enzymatic activities, not the glucose amount,were possibly the main factors of limiting mogroside Ⅴ biosynthesis.