The invention belongs to the field of medicinal preparations, and relates to a decataxel self-microemulsifying composition for injection and a preparation method thereof. The decataxel self-microemulsifying preparation comprises the following components by weight percentage: 1 to 20 percent of decataxel, 5 to 60 percent of oil phase, 10 to 90 percent of emulsifier, 1 to 30 percent of coemulsifier, and 0 to 10 percent of additive. The preparation method comprises the following steps: mixing the decataxel, the oil phase, the emulsifier, the coemulsifier and a stabilizer; performing ultrasonic treatment; stirring the mixture at a temperature of between 20 and 80 DEG C to ensure that the mixture is completely dissolved; and mixing evenly to obtain the composition. The self-microemulsion can be directly used and can also be diluted into products of any steady concentration to use by adding the moisture in any proportion. The composition reaches a human body through injection or oral administration, can spontaneously form a microemulsion with nanometer particle size when encountering body fluid, obviously improve the solubility of medicaments, increase the stability of the medicaments, and improve the bioavailability. The composition has the advantages of simple preparation process, high production efficiency, steady product quality, and easy industrialized large-scale production.