Tujuan penelitian ini untuk menghasilkan soal-soal kemampuan penalaran matematis materi bangun ruang sisi datar berkonteks Bengkulu yang terstandar: yang valid, memiliki keterbacaan baik, memiliki tingkat kesukaran dan indeks daya beda baik. Penelitian ini yang dilaksanakan pada tahun ajaran 2020/2021 ini mengikuti alur Tessmer. Subjek ujicoba adalah siswa kelas VIII SMP di Bengkulu. Sebelum prototipe soal dibuat, dilakukan analisis siswa, kurikulum, materi dan konteks. Telaah dan revisi soal dilakukan pada tahap experts review. Soal ditelaah oleh 3 orang validator dari sisi konten, konstruk, dan bahasa. Komentar dan saran validator pada proses validasi menjadi acuan untuk revisi soal. Hasil analisis validasi akhir para validator menunjukkan bahwa soal telah valid. Proses one to one pada 3 orang siswa kelas VIII yang masing-masing berkemampuan tinggi, sedang, dan rendah, Tergambar dari proses one to one bahwa maksud soal dapat terbaca oleh siswa. Bukti empirik mengenai tingkat kesukaran dan indeks daya beda butir soal diperoleh pada tahap small group, dengan cara mengujicobakan soal yang telah valid dan memiliki keterbacaan yang baik kepada 31 siswa kelas VIII SMP di Bengkulu. Skor siswa terhadap soal tersebut dianalisis secara kuantitatif. Hasil analisis menunjukkan bahwa 8 soal dikembangkan dikategorikan terstandar. Soal-soal ini dapat digunakan untuk melatih kemampuan penalaran matematis siswa SMP. Kata Kunci: Soal matematika, kemampuan penalaran matematis, konteks Bengkulu, bangun ruang sisi datar Abstract The purpose of this research was to produce standardized items on mathematical reasoning abilities in the Bengkulu context of flat-sided geometry: those that were valid, had good clarity appeal, had a difficulty level and a good discrimination index. This research, which was conducted in the 2020/2021 academic year, follows the Tessmer’ model. The test subjects were students of class VIII SMP in Bengkulu. Before the items prototype was made, an analysis of students, curriculum, material and context was carried out. The review and revision of the items were carried out at the experts review stage. The items were reviewed by 3 validators in terms of content, construct, and language. The validator's comments and suggestions in the validation process become a reference for revision of the questions. The results of the final validation analysis of the validators, showed that the questions were valid. One to one process for 3 students of class VIII, each of which has high, medium, and low abilities. It is illustrated from the one to one process that the meaning of the questions can be read by students. Empirical evidence regarding the level of difficulty and discrimination index of items was obtained at the small group stage, by testing items that were valid and had good readability to 31 grade VIII SMP students in Bengkulu. Student scores on these items were analyzed quantitatively. The results of the analysis showed that the 8 items developed were categorized as standardized. These items can be used to exercise the mathematical reasoning skills of junior high school students. Keywords: Item test of mathematics, mathematical reasoning ability, Bengkulu context, flat-sided geometry