To detect chemicals, we proposed a photonic crystal fiber (PCF) with hexagonal cladding and a hexahedron core (THz). Circular air holes (CAHs) in the vestibule provide the basis of the suggested sensor. To develop and evaluate our suggested hexahedron PCF sensor, we employed the finite element (FEM) technique and perfectly matched layers (PML), which utilized the optical parameters numerically. Here, 92.65%, 95.25%, and 90.70% are relatively sensitive, and confining losses are low. The value 5.40 × 10−08, 6.70 × 10−08 dB/m, and 5.75 × 10−08 dB/m for three chemicals such as Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330) and effective material loss (EML) of 0.00694 cm−1. The suggested Hx-PCF sensor has been successfully tested at 1 THz. We are certain that the suggested sensor's optimal geometric structure can be manufactured and that it can contribute to real-world applications in biomedicine and industry. In terahertz areas, our suggested PCF fiber is also suited for a wide range of medical signals and applications (THz).