The invention provides a silk waterproof agent, which comprises the following ingredients (by weight): 9-11 parts of sodium carbonate, 5-9 parts of acrylic resin, 3-8 parts of rosin, 5-8 parts of stearic acid, 2-4 parts of dextrin, 5-10 parts of calcium chloride, 3-8 parts of paraffin, 1-3 parts of sodium hydroxide, 1-2 parts of glass fiber reinforced polyester felt, 0.5-1.5 parts of sodium benzoate, 7-14 parts of aluminium potassium sulfate, 3-6 parts of polyvinylpyrrolidone and 150-200 parts of water. By selecting proper components at proper ratio, silk fabric processed and finished with the waterproof agent can have good waterproofness and better air permeability and softness.