In this study, dielectric permittivity of Opuntia were calculated and modelled in simulation program at 1.7-2.6 GHz. Waveguide measurement method was utilized to measure the scattering parameters of Opuntia in order to calculate dielectric constant in the predefined frequency range. The measurement system was set up with two waveguide adaptors WR430, an Anritsu network analyser (MS4624B), sample holder and a computer. The error coefficients were identified by Through-Reflect-Line (TRL) calibration technique and the accuracy of the system was checked. New Non-Iterative Method was used to calculate the dielectric constant from measured S parameters. Furthermore, according to the variation of humidity and frequencies, the dielectric constant and loss tangent of Opuntia was examined. Opuntia simulation model is defined in the Computer Simulation Technology (CST) program.