Indonesia is a country with a tropical climate characterized by high temperatures throughout the year with abundant sunlight and high air humidity. The caused of skin problems is due to harmful exposure such as UV rays, chemicals, and the environment factors. Bidara leaf (Ziziphus mauritiana L.) contains flavonoids act as antioxidants helping to maintain skin moisture by preventing the premature aging process which is characterized by thinning, wrinkles and dry skin. This research aims to evaluate the physical quality of gel preparations and the effectiveness of moisture from the gel preparations of bidara leaf extract with variations in concentrations of F0 0%, F1 0.5%, F2 1% and F3 3%. The physical quality of bidara leaf extract gel has a homogeneous preparation, pH in a safe range, high viscosity at F0, F1 and F2 but has good adhesion and dispersion that making it effective as a moisturizer. The moisture content in the preparation of Moisturizer gel of bidara leaf extract was determined by hydrate analyzer at varying concentration of bidara leaf extract (Ziziphus mauritiana L.) with consecutive humidity values of 54.3% (F0), 50.1% (F1), 55.56% (F2) and 62.94% (F3). The results of this research concluded that bidara leaf extract has the potential to be an effective natural ingredient as a moisturizer for providing moisture with variations in concentration indicating the level of skin moisture before and after the use of gel preparations. Keywords: gel, flavonoids, moisturizer, bidara leaves (Ziziphus auritiana L.)