Abstract: In order to solve the problems of low ground clearance, backward manure regulation technology and low working efficiency present in paddy fertilizing machine, a self-propelled high-ground-clearance spreader was designed for paddy variable-rate fertilization, the whole structure and working mechanism of the machine were introduced, the special chassis with high ground clearance, the fertilization disc and regulation device for fertilizing orifice were designed, the structures and parameters of main components of the machine were given, the software and hardware integrated control system which mainly consists of AT89C51 single-chip microcomputer (SCM) was designed, The fertilizing experiments in grounds and paddy fields showed that the angle for pushing fertilizer board was at -20°-40°, the minimum turning radius of the machine was less than 1.8 m, the height of fertilization disc from the ground was 1100 mm, the fertilizing width of machine achieved 14 m, working efficiency was up to 6 hm2/h, the experimental results indicate that the machine is suitable for self-propelled walking in paddy fields, and the design for the machine and its control system meets variable-rate fertilization requirements of widespread distribution and high efficiency in paddy fields.