Abstract: It is briefly introduced the proof-of-work consensus algorithm of blockchain technology. It is pointed out that the ambiguity of space-time will cause consensus divergence, and lead to reduced efficiency and waste of computing power. It is proposed to transmit common-channel signaling through BeiDou Navigation Satellite System (BDS) short message service, which can construct a scale-free network and avoid the asynchronous network ecology. It is also made a more in-depth discussion on the application of blockchain, and pointed out that all distributed behaviors can apply blockchain technology to solve the trust problem. Discussed that when blockchain technology is used in the real world, it should ensure the credibility of the ledger, the credibility of the physical and the credibility of space-time at the same time. It is proposed that the role of BeiDou is not only convenient and reliable to collect space-time tags, but also has the deeper meaning that the BeiDou positioning, navigation and timing (PNT) service has space-time credibility, including: service ubiquity, benchmark uniformity, space-time self-consistency, causal inevitability and consensus synchronization. Finally, the specific application of the BeiDou space-time blockchain is classified and introduced, including: full-chain supervision of processes, efficient resource sharing, and task crowd-creation collaboration.