The invention relates to an isoserine ester derivative or the salt of taxanes shown in the formula II; an R1, an R2 and an R3 in the formula are the same or different hydroxyl protecting groups. The invention further provides a preparation method for the compound and a method for further preparing an anticancer drug docetaxel according to the isoserine ester derivative. The preparation method forthe compound which is high in yield and simple in steps is suitable for the industrial preparation of the docetaxel.