This study aimed to find out the response of Trichoderma sp biological agents to Fusarium wilt intensity on the growth and yield of two onion plant varieties and the most appropriate dose of Trichoderma sp for controlling Fusarium wilt in two onion plant varieties. This study was conducted from February 2018 to April 2018, in the Greenhouse of Agriculture Faculty of Universitas Muhammadiyah Purwokerto. The design used in this study was a Completely Randomized Design (CRD) with two treatment factors, the first factor was onion plant varieties consisting of two types, namely Bima (V1) and Sumenep (V2), while the second factor was the dose of Trichoderma sp consisting of four levels. namely (T0) dose of 0 g / plant, (T1) dose of 20 g / plant, (T2) dose of 40 g / plant and (T3) dose of 60 g / plant applied three times: three days before planting, 20 days after planting (hst) and 40 days after planting. The results showed that the treatment of onion varieties significantly affected the growth variables such as number of leaves (16 days, 48 days and 64 days), total length of leaves (16 days, 32 days and 64 days), fresh tuber weight, fresh stover weight. and the dry stover weight which had no significant effect on the Fusarium wilt intensity variable, number of leaves (32 days), total leaf length (48 days) and number of tubers. Bima variety produced better tuber weight (3.07 g) compared to Sumenep variety (2.32 g). The treatment of Trichoderma sp had a significant effect only on the Fusarium wilt intensity variable aged 64 hst. The dose of Trichoderma sp 20 g per plant could reduce the Fusarium wilt intensity from the highest level of 47.50% to 17.00% while the second interaction treatment had no significant effect.