In order to alleviate the damage of high temperature stress on the seedlings of protected cucumber，the cucumber‘Jinchun No.4’was used as the test material，and the putrescine（Put），melatonin（MT），proline（Pro）and potassium fulvic acid（MFA）was mixed at different concentrations to investigate the effects of different concentration mixtures on high temperature resistance，photosynthesis，and antioxidant enzyme activity of cucumber seedlings，and screened out the optimal mixture for alleviating high temperature stress．The results showed that 8 mmol·L^-1 Put combined with 0.3 g·L^-1 MFA，1.5 mmol·L^-1 Pro and 50 μmol·L^-1 MT effectively alleviated the damage of high temperature stress on cucumber seedlings and the effect was the best comprehensively evaluated with the membership function method．The net photosynthetic rate increased by 160.71%，the leaf relative electrolyte leakage，malondialdehyde and H₂O₂ content decreased by 47.26%，68.00% and 40.64%，respectively．Furthermore，SOD，POD and CAT activities in cucumber leaves increased by 29.32%，31.66% and 52.16%，respectively．