Cornstalk was subjected to methanolysis in the presence of NaOH at 220-320 degrees C to afford soluble portions (SPs) 1-5 (SP1-SP5) and an inextractable portion (IEP). The maximum total yield (ca. 51%) of SPs was acquired at 300 degrees C with the same mass of NaOH and cornstalk. Under the same conditions, SP1 has the highest yield, followed by SP5 and SP2. The relatively volatile and less polar species in the resulting SPs and IEP were identified with a gas chromatograph/mass spectrometer (GC/MS). The polar species in SP1, SP2, and SP5 were further analyzed with a negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS). The analysis with GC/MS shows that phenolic compounds and alcohols are the dominant group components in SP1 and SP2 respectively, while the predominant compounds in esterified SP3-SP5 and IEP are esters. According to analysis with FTICRMS, thousands of compounds were detected in SP1, SP2, and SP5. Most of the compounds are O-n (n = 1-10) class species with double bond equivalent (DBE) values of 1-14 and carbon atom numbers of 5-35. The most abundant class species in SP1, SP2, and SP5 are O-3, O-3, and O-8, respectively. SP1 and SP2 are rich in O-2-O-4 class species with DBE values of 5-8, which may be attributed to lignin-derived compounds. Different from SP1 and SP2, SP, has relatively high contents of O-5-O-10 class species, corresponding to various acidic species. In addition, N1On, (n = 0-8) class species with DBE values of 3-14 were also identified, which should contain a pyrrole ring as the parent structure.