Provided in the present invention are a conjugate of polyethylene glycol and opioid as shown in general formula (I), and a pharmaceutical composition comprising the conjugate. By means of covalently bonding a plurality of opioids to a polyethylene glycol derivative, the present invention improves water solubility and pharmacokinetic property of the drug with a low addictive effect. PEG-(X-OP)m (I)
