Abstract: The communication and navigation fusion security positioning system based on the L-band communication signals of low-orbit satellites can effectively solve the shortcomings of satellite navigation in terms of anti-deception, signal processing, anti-interference and security. It is a supplementary backup to the existing Beidou satellite navigation system, which can effectively enrich the application scenarios of satellite navigation systems. This paper designs a safe positioning technology system and uses L-band fusion signals to broadcast navigation messages to achieve navigation positioning and timing. This paper simulates the impact of different carrier-to-noise ratios and receiver clock drift on positioning accuracy. The results show that when the receiver has clock drift and the carrier-to-noise ratio is 60dB-Hz, the positioning accuracy improves as the number of visible satellites increases. When the number of visible satellites is 3, the positioning accuracy can reach 5m, and the actual performance has been verified by developing a hardware prototype. The communication and navigation fusion security positioning technology system designed in this article has important reference value for the future construction and development of my country’s satellite Internet.