Sugar beet cyst nematode (Heterodera schachtii) is one of the most important pathogens in sugar beet in Iran. In order to control the biomass of this nematode, the effect of 6 species of isolates and identified fungi of the same nematode, including Neonectria macrodidyma, Colletotrichum gloeosporioides, Fusarium oxysporum, Simplicillium minatense, Simplicillium cylindrosporum, was investigated under laboratory conditions on cysts. Surface sterilization of H. schachtii species cysts with 0.5% hypochlorite for three minutes and several times washed with sterilized distilled water. A number of cysts were placed on one side with a sterile slider, and on the other side, at a distance of 2 cm, a 5 mm disc was inserted from the PDA medium, which was inoculated with a small inoculum for each isolate. The slides were prepared for each isolate in a sterile petri dish containing two layers of filter paper and five milliliters of distilled water sterilized. Petri dishes were placed at 25 ° C for two weeks. After this time, the slides were examined by magnifying 200, 400 and 1000 microscopes. In the study of sugar beet system parasitism by fungal isolates, all isolates were able to colonize H. schachtii cysts and a careful study of the cysts showed that these fungi were completely deployed on the cysts. The species of Neonectria macrodidyma, Colletotrichum gloeosporioides, Fusarium oxysporum, Simplicillium minatense showed the highest parasitism. In the species Embellisia astragali, it is well known that this indicates the potential for parasitism of this fungus. These fungi are recommended for further investigation in further research and generalization of these tests in vivo with the observation of the necessary points.