The aim of this work was to study the mechanism for the delaying effect of pre-harvest salicylic acid treatment on the ripening and softening of muskmelon fruits. The "Jin tian mi" muskmelon fruit was sprayed with 1.0 mmol/ L of salicylic acid for four times at different stages: young fruit stage (2 weeks after flowering), fruit enlarging stage (3 weeks after flowering), netting stage (4 weeks after flowering) and 48 h before harvesting. The post-harvest muskmelon was stored at low temperature ((7±1) ℃, relative humidity 85 %). The fruit firmness, cellulose content, protopectin content, cellulase (Cx), polygalacturonase (PG), β-glucosidase activities related to the ripening and softening of muskmelon were determined at regular intervals during storage. The results showed that the pre-harvest salicylic acid treatment (1.0 mmol/L) could effectively inhibit the decrease of firmness and protopectin content, delay the increase of soluble pectin content, inhibit the PG, Cx, β-glucosidase activities of muskmelon during storage. The ripening and softening of muskmelon were delayed effectively. In conclusion, salicylic acid treatment significantly inhibited the PG, cellulase and β-glucosidase activities to effectively delay the decrease of the fruit firmness, and therefore delayed the ripening and softening of muskmelon fruits.