Abstract: The established HPLC method used a C₁₈ column with methanol-water(75:25,V/V) as the mobile phase at a flow rate of 1.0 mL/ min. The detection wavelengths of furfural and 5-methylfurfural were 271 nm and 284nm, respectively, and their retention times were 4.969 min and 9.246 min. The furfural and 5-methylfurfural can be accurately deter mined at the same time by this method. The findings indicated that the method of determination offers the advantages of being simple and easy to operate, highly sensitive, and repeatable; the extraction method of furfural and 5-methylfurfural in rubberwood was optimized, and the contents of furfural and 5-methylfurfural in thermally modified rubberwood at different temperatures(125 ℃, 155 ℃, 185 ℃) were deter mined. It's showed that the contents of furfural and 5-methylfurfural in thermally modified rubberwood increased from 3.4 μg/g and 1.9 μg/g to 103.5 μg/g and 54.1 μg/g. This results would provide a theoretical reference for regulating the thermally modification technology of rubberwood.