According to modern orchard planting pattern and dynamic center of gravity of orchard sprayer, a mathematical model was established by theoretical calculation and test. The trafficability of large carton orchard sprayer was analyzed. The obstacle height curve with dosage was obtained. In the dosage range of 0~200L, the front wheels crossed obstacles reduced from the 200mm to 84mm. In the dosage range of 200~400L, the front wheels crossed obstacles reduced from the 84mm to 53mm. Rear wheel obstacle height was independent of machine parameters. Experimental were consistent with theoretical calculations. The results showed that the sprayer had outstanding trafficability in orchard.