The lignin in cortex and the whole cornstalk was isolated by simultaneously using xylanase and mild acidolysis, obtaining cortex EAL and the whole cornstalk EAL, whose chemical structures and pyrolysis characteristics were then determined respectively by quantitative ³¹P-NMR and thermogravimetry. The results show that the whole cornstalk EAL mainly consists of Guaiacyl unit and p-Hydroxyphenyl unit, while the cortex EAL mainly consists of p-Hydroxyphenyl unit ,that theTG and DTG curves of the two EALs are basically the same, and that the undecomposed lignin accounts for 12. 38% in the whole cornstalk EAL and 21. 60% in the cortex EAL at 800. 00 ℃ .