The present invention discloses a water-soluble docetaxel anticancer drug compound having the structure of Formula I below:in which R=—CH3, —CH2CH3, —CH2CH2CH3, or —CH2CH2CH2CH3; and n=5-500.The active moiety docetaxel in the anticancer drug compound is covalently conjugated to a polyethylene glycol monoalkyl ether through a linker diglycoloyl (carbonyl methoxyacetyl) to form the water-soluble docetaxel anticancer drug compound.The present invention also relates to a preparation method of the drug compound and use thereof.