Furfural residue (FR) is a low-cost by-product generated in the furfural production from corncobs, which is mainly composed of cellulose and lignin. In this report, hydrothermal carbonization (HTC) of deashed FR was conducted at various reaction temperatures (200, 220 and 240 °C) and reaction times (1-24 h). The chemical and structural properties of obtained biochars were investigated by elemental analysis, high-resolution solid-state 13C NMR, and X-ray photoelectron spectroscopy (XPS). Our experiments indicated that the biochar yields declined with increasing of reaction temperature and time. According to results from NMR and XPS, 240 °C is an essential temperature for biochar formation. At this temperature, changes in the surface properties initiated within 1 h, and the major transformation occurred within 8 h. The dominating change was cellulose fraction reaction forming furanic and aromatic structures in the biochar, which is faster at higher temperatures. In addition, these biochars showed high thermal stability below 300 °C according to thermogravimetric analysis. This study can provide a valuable approach for FR utilization