An agent for cosmetics, skin diseases and symptoms treatment and a preparation method thereof are disclosed, the method comprising: obtaining Cordyceps militaris as main ingredient subjecting to extraction process, impurity separation and precipitation process, dried solid formation process, backwash filtration process and dilution process, thus making an agent for skin external application. The Cordyceps militaris content ingredient thus extracted can be used for skin external application useful for inflammatory disease symptoms and achieves effective curing effect, while having multiple purposes and inventiveness by being able to provide beauty effect to normal skin.
