In order to evaluate the biological effect and interference of crop and weed in canola-faba bean intercropping in comparison with mono culture, an experiment was conducted in randomize completely blocks design with three replication at Ramin Agriculture and Natural Resources, University. In this experiment treatments were different compositions of canola (Brassica napus L. var. haylo) and faba bean (local cultivar). Plant densities (0, 20 and 40 plants per m2) for canola and four levels include (0, 20, 40 and 60 plants per m2) for faba bean in accordance with additive form mixed culture system respectively. Weed dry weight was affected by culture system and different levels of plant densities in mixed culture and there were significant difference 1%. Lowest weed dry weight was obtained in 20-60 and 40-60 plants m-2 canola-bean intercropping. In the intercropping parts only two species was observed while in the sole culture more than three species were exist. Results showed that with increasing in bean diversity, weed dry weight declines. According to our results, it is possible to control weed effectively by using intercropping system, but more studied is required. Diversity of weeds had been clearly affected. Results showed that only Beta and Malva species were existed in intercropping comparing to sole cultures that Brassica, Beta, Rumex and Malva were existed.