Corn stover (CS) was liquefied by using ethylene carbonate (EC) as liquefying solvent and sulfuric acid as a catalyst at 170 ◦C for 90 min. Polyurethane (PU) foams were prepared from liquefied corn stover (LCS) and polymethylene polyphenylisocyanate (PAPI) by oneshot method at a [NCO]/[OH] ratio of 0.6 in the presence of blowing agent, surfactant and co-catalyst. The effects of CS/EC ratio (w/w) on the structural, mechanical and thermal properties were studied by means of Fourier Transform Infrared Spectroscopy (FT-IR), thermal analysis (TGA/DSC) and universal tensile machine. FT-IR analysis indicated that urethane linkages were formed; free isocyanate groups existed in samples. All samples had a low thermal stability and decomposition occurred in four successive stages. With the increase in CS/EC ratio, tensile strength and Young s modulus first increased and then decreased, and elongation rate at break decreased. Properties of LCS-PU foams can be changed by varying the CS/EC ratio.