The improvement of organonitrogen compounds (ONCs) in methanol-soluble portions (MSPs) obtained from supercritical methanolysis of raw and pretreated rice straw (RS) with Trichoderma sp. AH was investigated. According to detailed analysis with positive-ion ESI FT-ICR MS and GC/MS, the molecular masses (MMs) of ONCs in MSPs of raw and pretreated RS range from 100 to 500 u and dominate from 300 to 450 u. The relative abundance of ONCs with MMs from 300 to 350 u in MSP of pretreated RS is higher than those in MSP of raw RS. Most of detected ONCs in MSPs of raw and pretreated RS are N2On, (n= 1-9) species with double bond equivalent values of 2-25 and carbon atom numbers of 4-35. The most abundant ONCs in MSP of pretreated RS are N2O4, while those in MSP of raw RS are N2O5. These results facilitate understanding the effect of pretreatment with Trichoderma sp. AH on the conversion and specificity of ONCs in methanolysis of RS and the application of MSP on production of transportation fuel. (C) 2017 Elsevier Ltd. All rights reserved.