The invention discloses a separating machine with a good impurity removing effect for agricultural grain. The separating machine with the good impurity removing effect for the agricultural grain comprises a shell, wherein a rotary motor is fixedly connected to the top part of the shell; a rotary shaft is fixedly connected onto an output shaft of the rotary motor; the bottom end of the rotary shaftpenetrates through the shell and extends to the inner part of the shell; a screen drum is arranged on the bottom part, located in the shell, of the rotary shaft; connecting rods are fixedly connectedto the left side and the right side of the rotary shaft; and one ends, far away from the rotary shaft, of the connecting rods are fixedly connected to the inner wall of the screen drum. According tothe separating machine with the good impurity removing effect for the agricultural grain provided by the invention, through the interaction of the rotary motor, the rotary shaft, the screen drum, theconnecting rods, a first sieve plate, a fan, a sliding rod, a sliding block, a reset spring, a second sieve plate, a drive motor, a drive rotary shaft and a rotary block, the grain is screened by adopting multi-stage screening and can be treated in a grading way, a screening manner is good, impurities of the grain can be removed thoroughly, a screening requirement of the high-quality grain can bemet, and great convenience is brought for a user.