The effects of probe-beam polarization direction on the THz detection in ZnTe were investigated experimentally. By keeping the THz radiation intensity unchanged, we observed two minimums with an interval of 1800 when the direction of the probe-beam polarization θ was changed from 0 to 360°. Non-zero THz radiation was detected in the middle of the two minimums ( θ =90°). The Jones Matrix method was employed to simulate the experiments by assuming the electro-optic effect in ZnTe under a THz field as an equivalent arbitrary wave plate. It was found that all the simulation results were in agreement with the experiments, except for θ =90°. A qualitative explanation based on the interaction between THz photons and TO phonons was presented.