In this work, interactions between cellulose and lignin during fast pyrolysis were studied to identify the impact of sample preparation on the light-products distribution. Cellulose-lignin interactions were investigated by Py-GC-MS with different temperatures (500, 600, and 700 degrees C), mixing ratios (mass ratio 1:1, and 2.1:1), and mixing methods (physical mixture and native mixture). Generally, cellulose-lignin co-pyrolysis could promote low weight molecular products (esters, aldehydes, ketones, and cyclic ketones) form cellulose and lignin-derived products (phenols, guaiacols, and syringols), while inhibit formation of anhydrosugars, especially the formation of levoglucosan. The native cellulose-lignin mixture had the most dramatic impact on the product distribution between the mixing methods studied. Finally, a statistic method-correlation coefficient R has been introduced to evaluate the interaction strength under different conditions, finding that mixing method played the most significant role on interaction, followed by temperature, and mixing ratio was the least significant. (C) 2016 Elsevier Ltd. All rights reserved.