The objectives of the study were to explore the effects of using the water-soluble mucilage of Monostroma nitidium to replace the humectant and half of the thickening agent on the rheological properties, color, storage stability, water-holding capacity, and film formation time of moisture masks thus prepared. Results showed that moisture masks containing water-soluble mucilage were pseudoplaxtic fluids. The apparent viscosity of these moisture masks decreased with increasing shear rate but increased with increasing concentration of the aqueous extracts used. The water-holding capacity of moisture masks containing 1% aqueous extracts and 1% hydroxyethyl cellulose (HEC) were similar to those containing 2% HEC and 5% 1-3 butadiene (humectant) but better than those containing 2% methyl cellulose (MC) and 5% humectant. The film formation time of moisture masks containing different concentrations of aqueous extracts decreased with increasing concentration of the aqueous extract used. The storage stability of a moisture mask containing 1% aqueous extract and 1% HEC was similar to that containing 2% HEC and 5% humectant and better than those containing 2% MC and 5% humectant. The safety test resulted in no erythema based on the Draize score test. The pH was between 7.1 and 7.5 for all moisture masks studied.