The invention relates to a deep moisturizing compound and a preparation method thereof. The deep moisturizing compound consists of the following components in parts by weight: 0.05-1 part of 
hyaluronic acid, 0.04-2 parts of transdermal 
fibronectin, 0.06-4 parts of 
ergothioneine, 4-40 parts of a dispersing agent and 5-60 parts of a 
solvent. The preparation method of the deep moisturizing compound comprises the following steps: dispersing the 
sodium hyaluronate and the 
ergothioneine by using the dispersing agent according to the ratio, then adding the material into the 
solvent, stirring the materials until the 
sodium hyaluronate and the 
ergothioneine are completely dissolved, finally adding the transdermal 
fibronectin, and completely stirring the material to obtain the deep moisturizing compound. According to the deep moisturizing compound provided by the invention, 
hyaluronic acid is used as a main functional substance for 
skin moisturizing, meanwhile, transdermal 
fibronectin is added to promote 
permeation and realize deep moisturizing, and finally ergothioneine is used as an auxiliary material to improve and repair a 
skin barrier and lock 
moisture in 
skin, so that comfortable skinfeeling can be provided, and skin health is facilitated.