Abstract: In a field experiment, the effects of rye (Secale cereale L.), hairy vetch (Vicia villosa Roth) and a mixture of rye and hairy vetch and method of killing them investigated on weeds control and tomato yield. Cover crops planted in fall of 2000 and 2001 in Varamin. Ten days before transplanting tomato cover crops controlled with glyphosate, mowing and harvesting. Rye had more biomass than mixture and vetch and the vetch had the least biomass. Cover crops was completely killed by glyphosate but regrew following mowing and harvesting. Cover crops treatments could not suppressed grass weeds. Mowing and glyphosate treatments of cover crops, reduced weeds density and biomass more than harvest treatment. Maximum tomato yield was in the mowing rye and mixture, such it increased yield more than 2 times compared to control. But in the hairy vetch the maximum tomato yield was in glyphosate treatment, which was 3 times compared to control. Generally, the results of this research showed that use of winter cover crops with suitable management is a good weed management system in tomato fields which increases efficacy of input and bring us closer to sustainable agriculture.