In order to study the effects of different sowing dates by some of companion crops on the weeds control, morphological traits and yield of corn Sc 504, a field experiment was carried out of Research Field at Tabriz University during 2010 growing season. Treatments were arranged in a factorial experiment using randomized complete blocks design with three replicatins. Factors was include four levels of companion crops (clover red (Trifolium pretense L.), hairy vetch (Vicia sativa L.), basil (Ocimum basilicum L.) and dill (Anethum graveolens L.)) sowing date companion crops with two levels (synchronic cultivation with corn and cultivation 15 days after corn). The result showed that the plant length trait was significantly influenced by companion crops and sowing date interaction, as maximum plant length was observed in synchronized planting corn with clover and minimum plant length was observed in cultivation of hairy vetch in 15 after cultivation of corn. There was significant difference between forage plants for leaf number, as maximum leaf number of plant was observed in the synchronic cultivation of corn with clover. Maximum and minimum grain yield of corn were 4062.9 kg.ha-1 and 3034.2 kg.ha-1 in cultivation of corn with clover and basil respectively. Biomass weed and maximum weed length in the maturity stage of corn were significantly affected by sowing date and companion crops interaction, as maximum and minimum biomass and weed length were significantly in the synchronic cultivation of corn with dill and the concurrent cultivation of corn with clover respectively and this is to rapid growth and high competitive power of clover in the early stage of growth. Also, with increasing of biomass weed and weed length, grain yield of corn linearly reduced. Synchronize cultivation of corn with dill was the best treatment than performance and weed control of other treatments.