Crop residues are one of the most problems, which face the Egyptian farmer. The quantity of crop residues in Egypt reached about 18.7 to 25 million Mg per year. The performance of chopping machine was tested under the following parameters. A) Four cutter head speeds ( 22.1, 25.6, 29.2 and 35.3 m/s ), B) Three number of knives were (2, 4, and 8 knives ) and  C) Three levels of corn stalks moisture contents were
( 35.0, 45.0, and 65.0 %).The performance of chopping machines as chopping length, degree of destruction, machine productivity and energy were measured. The final results of this study could be summarized as follows: Generally,  increasing the cutter head speed from (22.1 to 35.3 m/s) tend to increase percentage of chopping length 0.5 to 2.0 cm from (50 to 60 %), degree of destruction from ( 28.7 to 38.2 %) , machine productivity from (1.32 to 2.81 Mg/h), useful power from (2.19 to 3.86 kW), and with decreasing the unit energy required from (1.87to 1.37 kW.h/Mg) and chopping machine cost from (16.33 to 7.22 L.E/ Mg ) at number of knives 2 and corn stalk moisture content of 65.0 %.