The aim of this work is to estimate the energy and cost requirements for a developed machine of flax fibers separation.  This machine was fabricated in a locally workshop at Meet - Ali - Dakahleia Governorate  and testing in Tag EL- EZZ Agricultural Research Station, Dakahleia governorate The determined properties of performance machine were:- separating percentage of flax fibers, the energy and cost requirments.These parameters were investigated as affected by different machinery, and crop variables such as: separating drum speed (of 1.58, 3.52 and 8.21 m/s),straw feeding rate (of 2.0, 2.5 and 3.0 kg/ min).,and straw moisture content (of 8.42, 10.8 and 12.6 %,wb). The results indicated that; -   The best performance of a developed machine for separating percentage of flax fiber 75.7% were obtained  at drum speed of 8.21 m/s, feeding rate of 120 kg/hr and straw moisture content of 8.42%. -   The lowest values of energy requirements for separate one ton of fiber flax 13.94 kW.h/ton were obtained at drum speed of 1.58 m/s, feeding rate of 180 kg/hr and straw moisture content of 8.42%  -   The lowest values of cost requirement for separate one ton of straw flax 54.33 L.E/ton were obtained at drum speed of 1.58 m/s, feeding rate of 180 kg/hr and straw moisture content of 8.42%.