Abstract: Protoplast fusion between Exserohilum monoceras (EM) and Curvularia lunata (CL) was con-ducted with biparental inactivation technique. EM is highly toxic to barnyard grass but lower spore pro-ductivity , while CL is reversed to EM. The fusants were selected through observing the characteristics of morphology and biology , as well as the activity against weed. The results showed that co-function proto-plast of the 2 %Lywallzyme plus 2 % Snailase was the most effective way to its yield , 1.25 ×10⁶ for CL and 1.21 ×10⁶ for EM, respectively. The regeneration ratio of CL and EM treated by R3 medium was14.7 % and 13.2 % respectively. The protoplasts of CL and EMwere inactivated by UV for 30 s with the radiated distance of 20 cm and by hot water at 55 ℃for 5 min , respectively. 40 % PEGwas utilized to enhance the protoplast fusion. Three potent fusants were obtained , which were obviously different from the parental strains in spore morphology , mycelia growth rate , conidia yield and activity of inhibiting the barnyard grass root .