This study investigated the autohydrolysis pre-treatment prior to chemi-thermomechanical pulping (CTMP) process including the effects of autohydrolysis pretreatment with a lower severity on characteristics of the autohydrolysis liquor and hydrolyzed chips. The intensity of autohydrolysis, characterized by the severity factor, increased from 1.76 to 3.54, the hydrolyzed chips yield decreased from 99.0% to 86.7% and the xylose extraction yield increased from 0.8% to 44.0%. The content of holocellulose, pentosan and acid soluble lignin remained in the hydrolyzed chips decreased dramatically with increasing the treatment severity. After the autohydrolysis pretreatment, the resultant poplar chemi-thermomechanical pulp with a severity factor of 2.37 could obtain a 15.3 N m/g tensile index, 58.6% ISO brightness and a 2.39 cm(3)/g bulk. (C) 2014 Elsevier Ltd. All rights reserved.