Experiments were conducted in West Nubaria by using combine harvester with modified header to fit reaping alfalfa to increase productivity and minimize losses. The effect of forward speed of 3.20, 3.45, 3.78 and 4.32 km/h, cutting height of 3, 5, 8 and 10 cm, and cutter bar speed of 2.28, 3.18 and 3.78 m/s were studied. Measured performance indicatoss include field capacity and efficiency, cutting efficiency, productivity, total losses, energy requirements, operational and criterion function costs of reaping alfalfa were evaluated. The results indicated that, maximum cutting efficiency of 98.6%, minimum total losses of 3.28% and minimum criterion function costs of 91.54 LE/fed recorded with forward speed of 3.2 km/h, cutting height of 3 cm and cutter bar speed of 3.78 m/s, meanwhile maximum field efficiency was 90 % recorded with previous condition as if cutting height was 10cm. Also, maximum field capacity of 3.72 fed/h, while maximum productivity of 10.89 ton/h, energy requirements of 35.39 kW.h/fed, and harvesting operational costs of 53.4 LE/fed recorded with forward speed of 4.32 km/h, cutting height of 10 cm and cutter bar speed of 3.78 m/s.