The potato plant (Solanum tuberosum L.) is a horticultural commodity that can be used as a source of carbohydrates and has the potential to fulfill food needs. Plant pest organisms that are often found in potato plants are soil-borne pathogenic fungi with an attack intensity of 50% so they can cause crop yield losses of up to 100%. Controlling soil-borne pathogens of potato plants can use the biological agent Bacillus sp. One of the ingredients is an extracellular enzyme based on the abilities of bacillus sp. So this research aims to determine the effect of bacillus sp. can inhibit the growth of fusarium wilt disease. Bacillus sp. The bacteria used in this research were exploration bacteria from Wonokitri land, Pasuruan Regency, East Java, namely isolate I17. The method for carrying out this research is taking potato plant soil samples, isolation, rejuvenation of Bacillus sp. bacteria, 3% KOH test, catalase test, pathogenicity test, gram bacillus staining, antagonist test. Observation of the morphology of Fusarium sp. post in vitro antagonist test. Isolate I17 produced fusarium hyphae morphology that experienced abnormal development, namely bending, shrinking, lysis, twisting and curling. The research was carried out from December 2022 to April 2023 in the Health Laboratory, Department of Agrotechnology, Faculty of Agriculture, Veterans National Development University, East Java. Key words: Potato Plants, Fusarium sp, Bacillus sp INTISARITanaman kentang (Solanum tuberosum L.) merupakan salah satu komoditas hortikultura yang dapat dipakai sebagai sumber karbohidrat dan berpotensi untuk pemenuhan kebutuhan pangan. Organisme pengganggu tanaman yang sering ditemukan pada tanaman kentang adalah jamur patogen tular tanah dengan intensitas serangan 50% sehingga dapat menimbulkan kerugian hasil panen hingga 100%. Pengendalian patogen tular tanah tanaman kentang dapat menggunakan agensia hayati bacillus sp. Yang salah satu kandungannya adalah enzim ektraseluler berdasarkan kemampuan yang dimiliki bacillus sp. Maka penelitian ini bertujuan untuk mengetahui pengaruh bacillus sp. dapat menghambat pertumbuhan penyakit layu fusarium. Bakteri bacillus sp. yang digunakan dalam penelitian ini merupakan bakteri eksplorasi dari lahan wonokitri Kabupaten Pasuruan Jawa Timur yaitu isolat I17. Metode pelaksanaan penelitian ini yaitu pengambilan sampel tanah tanaman kentang, isolasi, peremajaan bakteri Bacillus sp., uji KOH 3%, uji katalase, uji patogenisitas, pewarnaan gram bacillus, uji antagonis. Pengamatan morfologi Fusarium sp. pasca uji antagonis in vitro. Isolat I17 menghasilkan morfologi hifa fusarium mengalami perkembangan yang abnormal, yaitu membengkok, mengecil, lisis, melilit dan keriting. Penelitian dilaksanakan dari bulan Desember 2022 sampai bulan April 2023 di laboratorium Kesehatan, Jurusan Agroteknologi, Fakultas Pertanian, Universitas Pembangunan Nasional Veteran Jawa Timur.Kata kunci: Tanaman Kentang, Fusarium sp, Bacillus sp