Abstract: The influences of the presvering time on the physical and chemical properties of the rice-straw were investigated and the disadvantageous factors to make the man-made board with the rice-straw due to presvering time were analyzed. It compared different properties including crystallinity, chemical composition and pyrogenation characteristics between the old rice-straw and new rice-straw by the wide-angle X-ray densitometer, the infrared spectrometry instrument and the thermo-gravimetric analysis (TG). The results show that the crystal degree of the old rice-straw is 25.6 percent lower than the crystal degree of the new rice-straw, the chemical composition and the pyrogenation characteristics of the old rice-straw are different from the new rice-straw. And these changes are disadvantageous to produce the man-made-board with the rice-straw.