Abstract: The study evaluates the lipolysis rate and extent of type Ⅲ lipid formulations using testosterone undecanoate as a model drug after digestion with in vitro lipolysis model, and studies the digestive regularity with optical microscope and electrical conductivity. The results showed that for testosterone undecanoate type Ⅲ lipid formulations with castor oil as oil phase and Transcutol HP as latent solvent, the lipolysis rate and extent were increased with the increase of oil phase proportion and were decreased with excessive proportion of surfactant, in which can see liquid crystal phase during lipolysis process. The lipolysis rate of type ⅢB lipid preparations with different surfactant were ordered as Labrasol > Tween 80 > Cremophor EL, but the rate of type ⅢA is different in quick digestion phase and slow digestion phase. The lipolysis extent of type Ⅲ lipid formulations with different surfactant were ordered as Cremophor EL > Tween 80 > Labrasol. These may be related to the digestive effect of pancreatic lipase on different surfactants. This study implied that the lipolysis rate and extent of type Ⅲ lipid formulations are greatly influenced by the proportion of oil phase and surfactant, and the surfactant structure. These factors will affect the in vivo digestion and should be taken into account when screening type Ⅲ lipid formulations.