In this letter, a hollow core ring based circular photonic crystal fiber (PCF) is explored and proposed with stably supporting terahertz (THz) orbital angular momentum (OAM) states transmission. The proposed PCF is discussed, investigated, analyzed and simulated with optical properties in a terahertz frequency spectrum ranging from 0.20 THz to 0.55 THz. The OAM and THz communication-based parameters of the fiber are deliberated extensively under various conditions through using the full vector finite element method (FEM). Some significant parameters of PCF like effective refractive index difference, dispersion profile, confinement loss, effective mode area, numerical aperture, power fraction and isolation effects are numerically discussed for the first time with their effects and applications on the THz OAM transmission. The mentioned PCF has supported 48 OAM modes with a large effective refractive index difference up to $10-3$. The confinement loss of the PCF around $10-10$ dB/cm, and the average dispersion profile variation is 1.0055 ps/THz/cm. Besides, the highest numerical aperture and power fraction of the PCF are 0.35 and 99.7882%, respectively. Also, a higher isolation power effect around 267 dB, and crosstalk less than −14 dB are obtained for the PCF. Moreover, this kind of PCF would be a robust candidate for efficient THz OAM transmission, high capacity and high feasibility of optical fiber