Terahertz region has become very attractive for new applications however, the materials that work in this region are very limited. Within the aim of providing a new instrument that can be used in this field, we designed and analyzed a new metamaterial (MTM) absorber and MTM absorber sensor for Sub-Terahertz region. As a first step, the structure was designed and the electromagnetic response of the design was analyzed. The perfect absorption with 99.9% absorption rate was achieved for the resonant frequency at 0.12 THz. After finding the resonant frequencies and absorption rates, the surface current and electric field distributions at resonance frequencies were gathered and then described. As a second step, sensory application of the proposed structure has been conducted. The material to be detected was added to the top of the structure as an overlayer (OL). The changes in reflection resonances by the mean of shift in resonant frequency and change in amplitude have been investigated as a function of the permittivity, thickness and loss tangent of the OL. As a result of that study, we proved that this unique MTM absorber can be used for detecting materials in Sub-THz regime.