Field experiments were carried out to evaluate a new developed reaper(Japanese harvesting reaper model KUBOUTA - AR 120)  on pulling flax crop. The effect of four pulling rollers speeds of 0.39 , 0.52 , 0.65 ,and 0.78 m/s , three machine forward speeds of 1.2 , 1.5 , and 1.8 km/h ,and three stalk moisture contents of 17.30 , 14.81, and 11.56 % . On actual field capacity, field efficiency, yield output, stalk damage and total stalk losses were undertaken. And also, an estimation of energy requirements and operating cost were determined. Results indicated that, the maximum value of actual field capacity, field efficiency and stalk yield output were 0.53 fed./h, 93% and 2.656 ton/h , respectively at pulling speed of 0.78 m/s , machine forward speed of 1.8 km/h and stalk moisture content of 11.56 %. However the lowest value of energy requirement of 1.97 kW.h/ton was recorded under the same mentioned above conditions. Meanwhile, the minimum values of stalk damage and stalk losses were 1.41% and 0.62 % , respectively at machine forward speed of 1.2 km/h , pulling speed of 0.78 m/s and stalk moisture content of  17.30 % .