Abstarct: Cucumber with the scientific name of Cucumis sativus L. is an annual plant of the genus Cucumis, of which about 30 species have been registered in Asia and Africa, and belongs to the Cucurbitaceaefamily.In order to investigate the effect of humic acid on growth and yield of greenhouse cucumber under drought stress of polyethylene glycol, four seed cultivars including Aria, Novin, PS64 and Isabel were used. Studies were conducted in two stages. In the first stage, the seeds of the four cultivars were evaluated in terms of root length, stem length, germination rate, germination percentage and seed vigor index under drought stress of polyethylene glycol. At this stage, two seed cultivars including Isabel cultivar were selected as the most resistant cultivar to drought stress and Aria cultivar as the most sensitive cultivar to drought stress. In the second stage, Aria and Isabel cultivars in terms of plant and fruit vegetative traits include stress effect, leaf area, stem length, stem diameter, absolute growth rate, relative growth rate, flowering time, fruit length, fruit diameter, fruit fresh weight, dry weight Fruit, tissue firmness, leaf nitrogen concentration, fruit nitrogen concentration, leaf potassium concentrationand fruit potassium concentration, under drought stress treatments caused by polyethylene glycol, humic acid treatment and interaction of polyethylene glycol and humic Acid was examined. Finally, it was found that the interaction of humic acid and polyethylene glycol on Aria cultivar in leaf surface traits, leaf nitrogen concentration, fruit length and fruit dry weight and in Isabel cultivar on leaf surface traits, fruit length and fruit dry weight were statistically statistically significant. It is significant at the 5% probability level. In general, drought stress caused by polyethylene glycol reduces the values in the quantitatively evaluated traits. Also, the effect of humic acid in most treatments caused an increase in the quantitative traits studied. Finally, the interaction between humic acid and polyethylene glycol was such that increasing the concentration of humic acid to some extent prevented the increase in drought stress following increasing the concentration of polyethylene glycol.