The invention relates to an ARM-based grain drier grain falling quantity detection device which comprises a grain falling system, a grain falling detection unit, an optoelectronic isolation unit, an ARM processor unit, a 485 communication module, a configuration software touch screen and a power supply module, wherein the grain falling detection unit detects magnetic steel on a belt wheel through a hall counting sensor, and the ARM processor unit detects the number of times of a PWM (Pulse-Width Modulation) signal falling edge, calculates the numbers of tipped hoppers attached to the belt wheel, then transmits the numbers of the tipped hoppers to configuration touch screen software, and visually displays the grain falling quantity of a grain drier on the configuration software touch screen. The ARM-based grain drier grain falling quantity detection device can acquire the grain discharge quantity of the grain drier in real time, visually display the grain discharge quantity on the configuration software touch screen, assists in calculating the content of moisture dried by the grain drier, and has the advantages of high precision, good stability, simplicity in operation, etc.