The invention relates to tubulin inhibitor phosphate ester and a composition and application thereof, and discloses a composition or pharmaceutically acceptable salt thereof. The formula Ia1 of the composition is shown in the speciation. The composition can generate drug prototypes with tubulin inhibition activity in a hydrolysis mode through an enzymatic and/or non-enzymatic mechanism. Compared with drug prototypes, the composition has better solubility and higher drug effects. The composition is suitable for being prepared into drugs of various dosage forms and widely applied to treating tumor diseases.