Autopsy 110 pigs in Dong Hy district, Thai Nguyen province, Trichocephalus spp. worms that collected from pigs to classify. The results showed that: all of them were Trichocephalus suis species only. Examination of samples of 750 pigs in Dong Hy district, there was 212 pigs infected with T. suis worms, the infectious rate was 28.27 percent, the intensity rate from light to severe (60.38 percent and 12.74 percent). The age, raising precedures, veterinary hygiene that effected to the prevalence of T. suis in pigs.