A low self-propelled sprayer for conventional orchard was developed in order to solve the plant protection mechanization. The power distribution unit was designed by theoretical analysis and virtual prototype to realize all working parts running independently. Eight shifts were designed by main and assistant gear-box. The sprayer could switch two-wheel drive to four-wheel drive according to running condition. Its minimum trafficable height was 1600mm. In the dosage range of 0~400L, the front wheels crossed obstacles reduced from the 87mm to the 70mm, and rear wheel obstacles height was independent of dosage. The minimum turning radius was about 2000mm. The simulation result by Creo Parametric 2.0 showed the sprayer worked steadily, and the velocity was between 1.5 to 16km/h. The effects of pesticide volume on centre of gravity and stability were little.