Abstract: In order to study the mechanism of softening in early-ripening apple cultivars，the fruit hardness，activities of amylase，cell wall hydrolysis enzymes and ethylene production were compared among three early-ripening apple cultivars. The results indicated that：① The fruit hardness of the three cultivars decreased during fruit development，however，in 75 days after blooming date the declining ranges were different in the three cultivars. The declining range of‘Liaofu’was 35% while that of‘Taishan Zaoxia’and‘Jizaohong’were 50% and 53%，respectively；②Activity of PE and amylase of the three cultivars showed little differences. The activities of PG and Cx in‘Taishan Zaoxia’and‘Jizaohong’were significantly higher than that of‘Liaofu’，and the activities of PG and Cx in the three cultivars were negatively correlated with fruit hardness；③ Ethylene production was positively correlated with the activity of PG and Cx during fruit development.

Key words: apple, early-ripening cultivar, fruit firmness, physiological index