Penelitian ini dilakukan berdasarkan kebutuhan akan adanya alat bantu bagi peternak maupun penyuluh dalam mendiagnosis penyakit pada ayam. Basis pengetahuan sepenuhnya diambil dari pengetahuan pakar yang dapat mendiagnosa dan menentukan nama penyakit yang diderita oleh ayam. Penelitian ini dibuat berdasarkan hasil analisis dengan membandingkan 4 jurnal internasional yang berjudul “Expert system of quail disease diagnosis using forward chaining method, An Expert System for Management of Poultry Diseases, Developling Mobile Expert Web-based System Using Brainstroming Method, Disease Diagnosis System”. Berdasarkan keempat jurnal tersebut dapat dikembangkan inovasi baru berupa Sistem pakar diagnosa penyakit ayam menggunakan metode Certainty Factor. Metodologi penelitian menggunakan wawancara dan studi literature sehigga dapat menggumpulkan data yang lebih lengkap. Sistem Pakar ini akan di implementasikan kedalam sebuah aplikasi mobile berbasis android dengan harapan memudahkan user dalam menggunakan karena dibuat kedalam aplikasi android sehingga bisa di install dalam handphone. Hasil akhir berupa suatu informasi data penyakit dengan nilai Certainty Factor/kepastian.Kata Kunci — Diagnosa Penyakit Ayam, Sistem Pakar, Android, Certainty FectorThis study was conducted based on the need for tools for farmers and extension workers in diagnosingdiseases in chickens. The knowledge base is completely drawn from the expert knowledge that can diagnose and determine the name of the disease suffered by chickens. This study was based on the results of the analysis by comparing four international journals entitled "Expert system of quail disease diagnosis using forward chaining method, An Expert System for Management of Poultry Diseases, Developing Mobile Expert Web-based System Using Brainstroming Method, Disease Diagnosis System". Based on the four journals can be developed a new innovation in the form of expert system of chicken disease diagnosis using Certainty Factor method. The research methodology uses interviews and literature studies so that it can collect more complete data. Expert System will be implemented into an android-based mobile application with the hope of facilitating the user in using because it is made into the android application that can be installed in the mobile phone. The final result is an information of disease data with Certainty Factor value/certainty.Keywords — Diagnosis of Chicken Disease, Expert System, Android, Certainty Fector