A one-dimensional optical biosensing metastructure (OBM) with graphene layers is presented in this paper. It is realized by coherent perfect absorption (CPA) and operates in the transverse electric mode. It shows a strong linear fitting relationship between the refractive index (RI) of the analysis layer and the frequency corresponding to the absorption peak, and the R-square is up to 1. Additionally, based on the principle of CPA, the OBM can realize the function of multiple cancer cell detection by adjusting the detection range by controlling the phase difference of coherent electromagnetic waves. Its detection ranges are 1.34-1.355 and 1.658-1.662. Thanks to its high-quality factor, great figure of merit, and low detection limit, whose best values are, respectively, 6.9 × 104, 1.2 × 104 RIU-1, and 3.6 × 10-6 RIU, the detection of weak changes in the RI of a cancer cell is possible. Additionally, its sensitivity can reach 26.57 THz RIU-1. This OBM based on CPA has major implications for advancing the study and investigation into the application of CPA. It also provides a simple and efficient approach to distinguish cancer cells and may be widely used in the biomedical field.