The invention relates to an oral pharmaceutical preparation of tadalafil, and application of the preparation on treating male erectile dysfunction. The oral pharmaceutical preparation is characterized in that the basic remedy is tadalafil or a salt thereof, wherein the specific dosage form of the preparation is an orally disintegrating tablet, a chewable tablet or an oral membrane preparation and other preparations capable of being released quickly in the oral cavity. Tadalafil is a slightly-soluble drug with relatively low bioavailability, so that the invalid dosage is relatively high, the drug can generate multiple adverse reactions, and the unreasonable prescription can cause visual impairment or visual loss. The research of the pharmaceutical preparation of tadalafil on increasing the bioavailability of the drug and reducing the adverse reactions is very important for wide application of tadalafil on treatment of male sexual dysfunction clinically. Secondly, through improvement on the compliance of the pharmaceutical preparation of tadalafil when a patient takes the drug, especially takes the drug in a non-swallowing manner in a water-free environment, the oral pharmaceutical preparation is a boon for a lot of ED (Erectile Dysfunction) patients. The oral pharmaceutical preparation of tadalafil disclosed by the invention is patient oriented, and produced through a large number of researches.