The important processes that follow the harvesting of various agricultural crops, especially the cereal crops, the process of sifting and separation of seeds from impurities, in order to get rid of the impurities that exist with the seeds in the first degree, and to get rid of the distorted and damaged seeds in the second degree. This study was aimed to study the effect of the sieve holes of a local industrial electric screening machine in the process of sifting and cleaning the seeds of some cereal crops, and evaluation the performance of this machine, and then determining the optimal sieve diameters for the seeds of crops studied and economically important in Syria. The active part of the machine, called the vibrator, consists of three layers of sieves and four gutters, the first sieve to get rid of large impurities (gravel, cloths, ...), the second sieve to extract the very large seeds, the third sieve moves the seeds to the graphite machine, It produces soft impurities (broken and small seeds). The second sieve was studied. The results showed that the best sieve of the cumin seeds with holes (0.8 mm) compared with actually used the sieve (1 mm). The best sieve seeds of holes (1.25 mm), compared with actually used the sieve (1.40 mm). The best sieve for local lentil seeds with holes (2 mm), compared with actually used the sieve (2.5 mm). The best sieve of chickpea seeds with holes (5 mm) compared with actually used the sieve (5.5 mm). Therefore, it is recommended to use the sieves with the holes shown above to screen the studied seeds instead of the actual sieves used in the screening factories due to their inaccuracy in the screening process because the diameter of these holes is not consistent with the sizes of the studied seeds.