The invention provides a process for preparing nanometer fecula powder body material, the process comprises first, adding technical-grade cornstarch in deionized water which contains a certain amount of dispersing agent to prepare homogeneous dispersion solution whose density is 5% to 15% (starch quality percentage), second, adopting high-energy ultrasonic wave to intermittently deal the solutionfor 3-5 hours under the condition of guaranteeing the system temperature which is not lower than 50 DEG C, third, placing the solution in a 40 DEG C to 50 DEG C water bath vessel to stir with a stirrer, and slowly adding acid into the solution till the density in the acid is 5% to 10% to react in constant temperature for one hour, fourth, pumping and filtering the solution which is reacted, and washing products with NaOH dilute solution to neutral, respectively washing with deionized water and absolute ethyl alcohol for several times, finally, abrading the samples in 60DEG C to 80 DEG C for 2-4 hours to get nanometer starch products. All the raw material of the process is sold in markets, raw material is wide, the reaction process can be controlled, reproduction quality is excellent, and production cost is low. The nanometer starch starches which are prepared by the invention takes ball shape, the size of the starch diameter is evenly distributed, and the major function group of original starch is not changed, and the starch is not polluted and can be used as carriers of biological medicine or food additives, thereby the invention has wide application prospect.