Onion cultivation through the common methods in East Azarbayjan , leads to low soil fertility, due to the use of fine sands to help germination of onion seeds . One way to solve this problem and reduce the production cost is onion transplanting .In addition , onion with short and superficial root must be grown in soil which is rich in nutrients and organic matters and consists of a soft and without clod structure. The present study was conducted to determine the suitable tillage method in preparing fine seed-bed and increasing the organic matters in top soil under semi-arid climate and loamy soil conditions. A split plot experiment based on randomized complete block design with three replications was used. The main plots concerning the primary fall-tillage were as following : 1- Moldboard plow in 25cm depth. 2- Chisel plow in 15 cm depth. 3- Disk harrow in 10 cm depth. Sub plots concerning the secondary tillage before transplanting were harrowing by disk and rotary tiller in 8-10 cm depth. During the experiment , some physical and chemical properties of soil , such as bulk density , penetration resistance (Con Index), organic matter , percentage of plant residues in various stages of operations and different depth of soil , plant establishment , bulb's weight and diameter average and yield were measured and analyzed. The following results were obtained : 1-The moldboard plow had the most effect on inversion of residues . When a soil- harrowing by disk or rotary tiller carried out after plowing , the residues spread in top and subsoil more evenly. Chisel plow had the least effect on burial of residues in soil. 2- Plowing by moldboard and chisel plow had the most effect on reduction of bulk density , penetration resistance and consequently increasing the soil porosity. Therefore , these implements with preparing of suitable conditions for plant establishment and growth , resulted in the highest yield . 3- In all treatments of secondary operation , the rotary tiller was more effective in soil pulverization than disk. 4-The treatments from viewpoint of organic matter in both 0-10 cm and 10-20 cm depth , because of experiment term shortness and undecomposing of plant residues, had no significant difference.