The development of single crystal chemical vapour deposition (scCVD) diamond membrane radiation detector is introduced in this paper. The fabrication of the diamond membrane radiation detector is illustrated, including the improvement of the diamond membrane sample and the usage of a homemade printed circuit board (PCB) to reduce the influence of the external noise and to build a complete device in a small volume. From the experimental results, the behavior of the diamond radiation detector using a beam of 2 MeV protons indicates that a 6.1 μm Optical-grade diamond membrane is capable of detecting the transmitted protons with low energy loss. The experimental results are fitted using the modified Hecht equation to introduce the avalanche effect.