Abstract: A dual-tone modulation intersatellite microwave photonics link model was presented including optical source, Mach-Zehnder modulator, erbium-doped fiber amplifier and photodiode. An exact analytical solution for any harmonic and intermodulation components at the output of the detector was deduced with the method of bessel expansion, fourier transform/inverse fourier transform and graf addition theory, thus, the expression of SNDR was derived considering the effects of third-order intermodulation distortion (IM3). The SNDR, fundamental and IM3 power varies with the radio frequency (RF) input power under different modulation modes was analyzed. Numerical results indicate that the SNDR, fundamental and IM3 power increases and decreases as the increase of RF input power, there is an optimum RF input power that maximize the SNDR. The SNDR of double sideband modulation is larger than single sideband modulation under the same RF input power and it is suitable for the application of intersatellite microwave photonics link.