In order to crush waste branches with the diameter not exceeding 30 mm trimmed from mountain orchards and other garden places, into sawdust with a length not exceeding 30 mm and particle size not exceeding 5 mm, a small moveable thick hammer branch grinder was designed and improved, where branches may be fed by the feeding roll through a single-channel, and crushed in a non-repetitive way. On the basis of hammer crushing principle, the size, structure and working methods of the feeding devices, the rotor assembly and hammer were redesigned and improved, which achieved the design goal of the grinder. The crushing experiments to determine the spindle speed showed that the optimum spindle speed range for the grinder is 2050-2200 r/min, and the crush confirmatory experiments showed that when the spindle speed is 2100 r/min ,the productivity can reach 0.851 m3/h, and the unit energy consumption will be as low as 3.162 kW·h/m3.The parameters are ideal, and the crushing effect is good.