This paper deals with the refining property and fiber morphology of thermo-mechanical pulp（TMP） of masson pine modified with laccase/mediator system.The results indicate that,after the modification with laccase/mediator system,the middle lamella and even the primary wall of the fibers corrodes,the content of lignin on the fiber surface decreases,and more layer structure rich in carbohydrates are exposed to water.Thus,the water absorption of the fibers increases,the softness and swelling of the fibers improve,and the refining property improves to some extent.Moreover,it is found that the breaking length and tearing index of the paper sheet formed by the fibers with laccase modification increase by 37.30% and 47.33%,respectively,the bulk decreases by 20.33%,and the contact angle also decreases.It is thus concluded that the laccase modification is effective in improving the refining property of masson pine TMP and the strength of paper sheet.