The invention provides a heavy-duty mine car cargo tank coating device. The heavy-duty mine car cargo tank coating device comprises a coating base, inverted-T-shaped supporting rods, grooves, conveying rollers, first supporting plates, a guided supporting frame structure, a blowing dust collection frame structure, an observable drying frame structure, a collectable adsorption scraping frame structure, conveying motors, fixed plates, wing bolts, arc-shaped plates, a spraying box, a coating pipe, a coating box, a coating pump, an air pump, a connecting pipe, a suction fan assembly and a supporting roller. The inverted-T-shaped supporting rods are connected to the four corners of the lower end of the coating base through bolts. Through arrangement of a U-shaped supporting frame, adsorption blocks, a scraping seat, a scraping blade, the coating base, the grooves and the supporting roller, the heavy-duty mine car cargo tank coating device can scrape off coatings on the surfaces of the supporting roller through contact of the scraping blade and the supporting roller in the coating process of cargo tanks, and the situation that the coating quality of the cargo tanks is affected after different types of coatings are mixed is avoided.