Fulvestrant or fulvestrant derivative oily preparation and preparation method thereof. The oily preparation comprises: fulvestrant or a fulvestrant derivative, the content being 10mg/ml to 170 mg/ml; a lactate compound, the content being 5% to 80% of the total weight of the preparation; vegetable oil or artificially-synthetic oil (grease) ester; a pain-killer; and an optional antioxidant.