To solve the optical handling of microwave signal problem in satellite communication, the inter-satellite microwave photonic link is presented. Two parallel dual-electrode Mach-Zehnder modulators are utilized to achieve the inter-satellite optical transmission and frequency down conversion of microwave signals based on optical carrier suppression modulation. The solution for any harmonic and intermodulation components of receiver signal is derived with Bessel expansion, and the relationship formula between carrier number and output signal to noise and distortion ratio (SNDR) is deduced. The optimum modulation indexes are obtained with curved surface projection method. The effects of carrier number to optimum modulation indexes, optical emission power and SNDR are analyzed. The results show that, the optimum modulation index of modulator with local oscillator can remain unchanged while the carrier number changes. When the carrier number increases, the optimum modulation index of modulator with signals and optimal SNDR both decrease and the optical emission power will increase.