Atomic polarizability reflects the response characteristic of atoms to the applied external electro-magnetic fields or optical fields. The wavelength (or frequency) of the applied external electro-magnetic fields or optical fields with which atomic dynamic polarizability equals to zero is so-called the tune-out wavelength (or frequency). Technology of quantum manipulation based on tune-out principle also has important applications in quantum precision measurement, quantum computation and quantum communication, and the related research topics include the measurement of basic physical constants, strong interaction and so on. The tune-out wavelength of atoms of the low-lying states is mainly the optical frequency bands, and the theoretical calculation and experimental measurement are gradually mature. For Rydberg atoms in the highly excited states, theoretical calculation is difficult due to the high density of Rydberg atomic states. And experimental measurement is also difficult because the separation of adjacent energy levels is small, mainly in microwave and terahertz frequency bands. In this paper, we have designed a measurement device of Rydberg atoms in a cesium vapor cell at room temperature. Amplitude-modulation electromagnetically-induced transparency (AM-EIT) spectroscopy is employed to measure tune-out wavelengths. The two-photon cascade excitation scheme is used to prepare Rydberg state of cesium atoms, and EIT spectrum detects Rydberg state. The AM-EIT signal of Rydberg atoms is obtained by continuous scanning the microwave frequency. At the near resonant microwave transition wavelength, the AM-EIT signal is strong due to strong microwave-atoms coupling and large polarization. At the tune-out wavelength, the AM-EIT signal is very weak because the total contribution of neighboring energy states to the polarization of the target state is zero. We set up a simplified three-level model to calculate tune-out wavelengths. Taking Rydberg state of cesium atoms as an example, the difference between the measured tune-out frequency of the two resonant microwave transitions and the tune-out frequency calculated by the simplified model is within ±90 MHz. In conclusion, the theoretical results are in good agreement with the experimental results.