Abstract: In preparation for using Cn band as a new standard satellite navigation band， this paper presents the radio frequency compatibility analysis between Cn band Satellite Navigation signal and Microwave Landing System signal. Through the calculation of the Power Flux Density （PFD） values， the interference for Cn band satellite navigation downlink signal from single in-view space stations on MLS service is evaluated. Simulation analysis of the interference for MLS DPSK-data word signal and scanning signal on Cn band satellite navigation signal is based on the Spectral Separation Coefficient and equivalent Carrier-to-Noise Ratio methodologies. The required separation distances to avoid harmful interferences， on basis of the space propagation model of signals， are summarized. This study will certainly benefit the design of Cn band satellite navigation signal and guide the site selection of its earth stations.