Trichoderma species have been used as biological control agent against soil-borne plant pathogenic fungi. Soil samples were collected from tobacco seedbeds of Mazandaran province. Common media including PDA, WA, CMA and Davet s selective medium were used to isolate fungi from soil samples. Fungal obtaining isolated after prepare pure culture were identified at genus level by using Bissett key. Among 72 soil samples, 60 isolates were belonging to genus Trichoderma species. Because of the importance of genus Trichoderma as biocontrol agent, its species were recognized. Species were identified according to their macro morphological and micro morphological characters including feature and size of conidiophores, phialid and phialospere by using keys written to identification species of this genus. Dual culture of antagonistic fungi and pathogen on PDA plate revealed that the antagonists reduced and inhibited the mycelial growth of Sclerotinia sclerotiorum. Mycelial growth inhibition rate of Trichoderma species against. S. sclerotiorum were different and it ranges between 51/25%-94%. Identified Trichoderma spp. was including: T.harzianum, T.citrinoviride, T.longibrachiatum, T.koningii, T.virens, T.atroviride, T.ghanense. In greenhouse study, isolates Tr6a, Tr9b, Tr29-1 and Tr102 were effective in disease reduction percentage by 87.5, 81.25, 56.25 and 68.75 respectively. Also, these isolates caused in height, shoot and dry weight increase.