In this study, new expressions for wave structure functions (WSFs) for optical planes and spherical waves propagating in plasma turbulence are derived based on the refractive index undulation power spectrum of hypersonic plasma turbulence and Rytov approximation theory. On this basis, the mathematical expressions for plasma turbulence modulation transfer function (MTF) for optical planes and spherical waves are obtained using WSF expression. The mathematical expressions describe the attenuation effect of plasma turbulence on optical imaging systems. The effects of different wavelengths, turbulent outer scales, and refractive index undulation variance on plasma turbulence MTF were calculated and analyzed. Results show that increasing the incident wavelength reduces the effect of plasma turbulence on the imaging system. Moreover, increasing the turbulence outer scale and reducing the refractive index undulation variance can also improve the imaging results.