Clostridium thermocellum can degrade lignocellulosic materials to produce hydrogen, acetate, lactate and ethanol, and surfactants have been proven to have the ability of increasing the enzymatic hydrolysis of cellulosic substrates. Here, the effects of surfactants on the fermentation of spent mushroom compost by C. thermocellum were investigated and their underlying mechanisms were preliminarily studied. PEG8000 and JFC-E had different effects on the fermentation performance of spent mushroom compost. Under optimum conditions, PEG8000 increased the hydrogen production by 59.78%, compared to the control without surfactant, while JFC-E improved the accumulation of glucose and xylose rather than hydrogen yield. PEG8000 also had different impacts on the bioconversion of non-lignin substrates (Avicel, carboxyl methyl cellulose and filter paper). With added PEG8000, the hydrogen production was improved when using Avicel as the substrate, and with PEG8000, the yields of products and sugar accumulation were different from those without PEG8000, indicating that PEG8000 may increase the hydrogen yield by shifting the microbial metabolism. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.