Abstract: Effect of high pressure treatment on the crystalline properties of acorn starches was studied by RINT2000 vertical goniometer. Results show that high pressure treatment can not change the crystal type; high pressure treatment has a definite effect on the crystal type of acorn starches. The pressure treatment has the best significant effect on the crystallinity, more significant effect on the micro-crystallinity, and significant effect on sub-crystallinity of the starches. High water content has more significant effect on the crystallinity during high pressure treatment, when the water content of acorn starchs is higher, the effect is more significant. When being high pressure, the intensity of its pressure has significant effect on the crystallinity of the crystalline and micro-crystalline. When the stronger the pressure becomes, the worse crystallinity will decrease.