Penelitian ini bertujuan untuk 1) menghasilkan instrumen penilaian berbasis komputer yang layak untuk mengukur kemampuan kognitif peserta didik SMA, 2) menguji efektivitas instrumen penilaian berbasis komputer yang dikembangkan untuk mengukur pengetahuan Fisika peserta didik SMA, 3) mengukur tingkat kesiapan peserta didik dalam menghadapi ujian nasional berbasis komputer.Penelitian ini menggunakan model Research and Development (RD). Model RD terdiri atas tiga tahap utama yaitu: tahap pendahuluan, tahap pengembangan dan tahap evaluasi. Pada tahap pendahuluan telah diidentifikasi permasalahan penilain pembelajaran fisika berbasis komputer. Tahap pengembangan telah dilakukan pembatan disain instrumen peniliaian fisika berbasis komputer, validasi produk, revisi produk dan uji coba produk secara terbatas. Pada tahap evaluasi telah dilakukan uji coba secara luas, revisi produk, dan pembuatan produk akhir. Uji statistik deskritif digunakan untuk mendeskripsikan hasil aplikasi penilaian pengetahuan berbasis komputer.Hasil penelitian ini: (1) Instrumen soal yang dikembangkan layak untuk untuk mengukur kemampuan kognitif peserta didik SMA, (2) instrumen penilaian berbasis kompunter lebih efektif dan efisien untuk mengukur kemampuan pengetahuan Fisika peserta didik SMA daripada paper and pencil test, (3) Peserta didik 58,67% sudah siap menghadapi tes berbasis komputer ,34% peserta didik belum siap melakukan tes berbasis komputer dan 7,33 % tidak siap melakukan tes berbasis komputer. Kata Kunci: Penilain berbasis Komputer, FisikaThe Development of Computer–Based Assessment of Physics Science to Improve Readiness of Students in Dealing Computer–Based National Examanation AbstractThis research aims to 1) produce computer-based assessment instruments eligible to measure the cognitive abilities of senior high school students, 2) test the effectiveness of computer-based assessment instrument developed to measure the knowledge of physics in senior high school students, 3) measuring the level of readiness of students in dealing computer-based national examanation. This research uses a model of Research and Development (R D) which consists of three main stages: the preliminary stage, the stage of development and evaluation phase. At the preliminary stage has been identified problems of computer-based assessment of learning physics. At the development stage has been carried out the design manufacture of computer-based assessment instrument physics, product validation, product revisions and testing of products on a limited basis. In the evaluation stage has been tested extensively, product revision, and the final product. Descriptive statistical test used to describe the results of the application of computer-based knowledge assessment. The results research show that : 1) computer-based assessment instruments eligible to measure cognitive abilities of senior high school students, 2) computer-based assessment instruments are more effective and efficient to measure the students knowledge of physics in senior high school rather than paper and pencil test, 3) 58.67% of students are ready to face computer-based test, 34% of students not yet ready for the computer based test and 7.33% are not ready to perform the test based computer.Keywords: Computer-Based Assessment, Physics