This research aims to study effects of some factors on design of rice straw-bales chopper to solve the operation problems such as un-continuous rice-straw feeding rate to a cutting unit, the feeding-platform height and the rice-straw cutting size. The experiments were conducted to determine the optimum operation factors to achieve the straw lengths desired for the animal feeding and compost. The studied factors were type of knives (free, fixed-curved and free fixed-curved), chopping-drum speeds of 1450, 1750, 2050 and 2350 rpm (34.16, 41.23, 48.3 and 55.37 m/s) and feeding-mechanism speeds of 0.26, 0.31, 0.35 and 0.42 m/s. The Experiments recorded that increasing chopping-drum speed from 1450 to 2350 rpm, decreased the mean straw cutting-length from 9.12 to 4.92, from 7.95 to 3.65 and from 7.31 to 3.31 cm using free, fixed-curved and free fixed-curved knives type respectively at all tested feeding-mechanism speeds. The maximum chopper productivity of 1.2 Mg/h was recorded by using chopping-drum speed of 2350 rpm and feeding-mechanism speed of 0.42 m/s, meanwhile, the minimum chopper productivity of 0.92 Mg/h was recorded by chopping-drum speed of 1450 rpm and feeding-mechanism speed of 0.26 m/s at all cutting-knives type. The results revealed that increasing chopping-drum speed from 1450 to 2350 rpm, increased the chopper power-requirement from 3.51 to 7.12, from 4.15 to 7.75, and from 4.78 to 8.23 kW, while, increasing chopping-drum speed from 1450 to 2350 rpm, the chopper specific-energy increased from 3.81 to 5.93, from 4.5 to 6.46 and from 5.19 to 6.86 kW.h/Mg by using free, fixed-curved and fixed-curved knives type respectively at all tested feeding-mechanism speeds.