the influence of drug dissolution rate: ① particle size: small particle size, high dissolution rate, which is beneficial to absorption. ② Wettability: The contact angle of hydrophobic drugs is favorable for dissolution. Surfactant is added to promote wetting. ③ Polymorphism: the order of absorption speed is unstable > Metastable > Stable crystal form; Amorphous drugs dissolve faster than crystalline drugs. ④ solvate: organic solvate > Anhydrous thing > Hydrate. ⑤ Methods to improve dissolution rate: nano-powder, surfactant, salt or hydrophilic prodrug, solid dispersion, cyclodextrin inclusion compound and phospholipid complex.