【Objective】Guiken 3 and Hass are the two main avocado, Persea ameriana, cultivars in China. The differences in postharvest physiology and nutrient components between Guiken 3 and Hass avocado during the ripening process were compared. 【Method】 The fruits of Guiken 3 and Hass were harvested and allowed to ripen at 20 ℃. The physiological changes in postharvest and nutrient components during the fruit ripening process were determined.【Result and conclusion】 A climacteric ethylene peak of Guiken 3 was observed on the 5th day，one day earlier than that in Hass, and the peak value was about 5 times higher than that of Hass. During the ripening process, pectinmethylesterase and cellulase activities of Guiken 3 pulp were higher than those in Hass, and propectin pectin and soluble pectin contents were lower than those in Hass. Moreover, cell membrane permeability of Guiken 3 pulp was higher and the pulp firmness was lower than those of Hass. The oil, protein and carotenoid contents increased during the fruit ripening process, while soluble carbohydrate content decreased. The oil content of Hass pulp remained at a higher level during the ripening process than that of Guiken 3 pulp. The oil content reached 21.0% and 11.7% in the ripened Hass and Guiken 3 fruits, respectively. But the soluble protein, soluble carbonhydrate and carotenoid contents of Hass pulp remained at lower levels compared with those of Guiken 3. In the ripened Hass fruits, the contents of soluble protein and carotenoid reached 9.1 mg·g^-1 and 6.2 μg·g^-1, respectively, while in Guiken 3, they were 17.7 mg·g^-1 and 7.8 μg·g^-1, respectively. These results indicate that Guiken 3 avocado fruits ripen and soften more quickly than Hass, and Hass has a higher contents of oil, while Guiken 3 has higher contents of soluble protein and carotenoid.