The primary objective of this investigation was to provide database about the physical properties ( length , width , mass    of 1000 –seeds, volume , percent of sphericity, geometric diameter, arithmetic diameter, transverse surface area, flat surface area, true density and bulk density ) and mechanical properties ( friction angle, angle of repose, hardness, and terminal velocity) of clover seeds. Also, to study some parameters affecting cleaning unit such as diameter of holes, air speed, sieve tilt angle, sieve oscillation with feed rate of 500 kg/h, and moisture content of 10.5 %. Three different varieties of clover seeds: AL-Mesqawi, AL-Khadrawi and Al-Seadi which are considered as the most important clover seeds in Egypt.The results indicated that :Length, and width, for AL-Mesqawi, AL-Khadrawi and Al-Seadi were 2.40, and 2.10; 2.45and 2.12 ; 3.00 and 2.10 mm respectively. percent of sphericity and Volume for AL-Mesqawi, AL-Khadrawi and Al-Seadi were 87 , 86 and 70 %  ; 4.55 , 4.65 , and 5.36mm³  respectively.                 Friction  angle with  three sheets from stainless steel, metal and wood was 24 , 31and  36 degree; 24, 31, and 37 degree;25, 32 and 38 degree for AL-Mesqawi, AL-Khadrawi and Al-Seadi respectively. Terminal velocities for AL-Mesqawi, AL-Khadrawi and Al-Seadi were ,15 , 15 and 16 m/s respectively.                 From the study , the principals parametere of sieve unit, the diameters of round sieve hole were , 3.0, 3.0 and3.5 mm for AL-Mesqawi, AL-Khadrawi and Al-Seadi respectively. The main results of this study can be summarized as follows: - The cell area depends on the physical properties of seeds clover and its shape depends on the percent of  sphericity of seeds. The separation  can  be achieved on the basis of length using a  screen aperture of 4 mm diameter, and percentage of sphericity of approximately 85 % on length for circular hole. - Terminal velocity to suspend clover seeds ( variety AL-Mesqawi, AL-Khadrawi and Al-Seadi) was 16 m / s. - The results showed that cell shape, sieve tilt angle, sieve oscillation and air speed were the main factors that affect purity and total losses in cleaning. - The results showed that cell shape, sieve tilt angle, sieve oscillation and air speed were the main factors that affect purity and total losses in cleaning. The purity increased by increasing air speed, sieve tilt angle and sieve oscillation. Total losses increased by increased air speed, sieve tilt angle and oscillation. -The optimum performance was at air speed of 6 m/s , moisture content of 10.5 %, sieve oscillation of 250 rpm, sieve tilt angle of 3⁵ , round shaped sieve 4 mm diameter, and feed rate of 500 kg/h. purity at these conditions was 99 % and total losses 1 %.