The invention discloses a high-precision grain sample blanking and collection method specifically including the following steps of importing seeds into a slope hopper; allowing seeds to fall freely due to gravity, and allowing some seeds to fall into a measuring cylinder from a middle round mouth of the slope hopper and the remaining seeds to slide into a weighing cylinder along a slope; discharging respectively through the weighing cylinder and the measuring cylinder; resetting the weighing cylinder and the measuring cylinder to be empty and return to the starting position. The high-precisiongrain sample blanking and collection method mainly comprises the two parts of weighing cylinder and measuring cylinder to respectively discharge, and has the advantages that discharge effect is excellent due to the overall use of step-by-step discharge, and discharge accuracy is high with the whole process unaffected by each other at the same time, thus enabling the efficiency to be higher.