This paper uses the two-dimensional particle-in-cell simulation program EPOCH to verify the feasibility of the relativistic electron beam probe in diagnosing the electrostatic wave generated by stimulated Raman scattering. The results show that the electron beam probe will produce density modulation in the transverse direction of the electron beam probe after passing through the electrostatic wave’s electric field. The density modulation is periodically distributed and moves along the propagation direction of the electrostatic wave. The wavenumber of the density modulation corresponds to the wavenumber of the electrostatic wave. And the moving speed corresponds to the phase speed of the electrostatic wave, so it can be used to deduce the temperature and density of electrons under certain conditions. In the process of diagnosing electrostatic waves, the beam length of the electron beam probe must be shorter than the wavelength of the electrostatic wave or the exposure time of the diagnostic equipment must be less than the period of the electrostatic wave. The research in this paper provides a new method of directly diagnosing the temperature and density of electrostatic waves and electrons, which is of great significance for promoting the experimental research of stimulated Raman scattering and other laser plasma instabilities.