Abstract: Calendula officinalis is well-Known for medical, ornamental, and cosmetic uses. This plant has a variety of secondary metabolites (carotenoids, flavonoids, steroids, and terpenoids) that may be a source of antioxidants. These chemical components have various biological effects, such as antioxidant, anti-cancer, and anti-inflammatory activates. However, salinity stress limited the growth and productivity of Calendula officinalis as a result of physiological, biochemical, and morphological changes. Hydrogel use is an alternative for reducing the harmful impact of salt stress. So, this study aimed to estimate the effects of hydrogel applied in Calendula officinalis grown under salt stress. The experiment design includes three replications, a factorial randomized complete block design with two factors, using three concentrations of salinity (0, 200 and 3000 ppm) and three different levels of hydrogel polymer (0, 0.4, and 0.6% w/w) both added to the soil before planting and the interaction between them. The results observed that the most significant increase in growth and flowering parameters was treatment with hydrogel alone at 0.6% (w/w). Similarity, salt tolerance index (STI), photosynthetic pigments in fresh leaves, lycopene and β-carotene pigments in fresh petals, elements (N, P, and K) in shoot and root and protein analysis. Whereas the highest content of total sugar, phenol, proline, antioxidant enzymes activity Catalase (CAT),Superoxide dismutase (SOD), and Peroxidase (POD), content of elements (Na and Cl), and decreased of some protein bands in the leaves and total free amino acid content was obtained from plants treated with salinity at 3000 ppm alone without hydrogel. In addition, the interaction between hydrogel at 0.6% (w/w) and 3000 ppm salinity showed a positive impact on most growth parameters and chemical analysis as well as overcoming the negative effect of salinity stress of Calendula officinalis L. plant.