provided are polyethylene glycol drug conjugates of general formula , or and pharmaceutical compositions and a use thereof . the conjugates are formed by combining low molecular weight polyethylene glycol with 2 - 4 drug molecules . the conjugates can interact with receptor dimers or polymers , thereby improving the in vivo distribution of the drug , changing the oil and water distribution coefficient , enhancing the pharmacological activity , reducing the blood - brain barrier permeability of the drug , and improving the bioavailability of the drug .