With the expansion of the application of blockchain technology in the socio-economic fields

increasing attention has been paid to the security of blockchain. This paper proposes a security risk assessment method for blockchain

which quantifies the security risk of blockchain from the aspects of technical architecture and hash rate. At first

we build the Blockchain Trusted Computing Base (BTCB) model based on the technology architecture. Then

we design a sensitivity analysis method combined the AHP and paired comparison to assign security weights to each security risk factor. Finally

we construct a security risk assessment model. In the experimental part

we use this model to score 15 common public-chain blockchain projects

and conducte comparative analysis with the evaluation data of four blockchain rating agencies with high market recognition. The experiment results verify the feasibility of this method.