The fixed key and international cryptographic algorithm used in the traditional security bus have some uncontrollable factors and security risk in its design. A novel method of a security parallel bus is proposed to solve the security risk of traditional bus transmission. The key generation mechanism and ring oscillator physical unclonable function are designed in the security parallel bus. The key is generated by the SM3 algorithm with the input of the physical unclonable function and random number generator. The transmitting data on the bus is encrypted using SM4 algorithm. When encrypting，random numbers are used to fill plaintext for security reasons. These guarantee the security of bus data transmission. The bus implemented by this security mechanism can effectively resist the intrusive analysis，the replay attack，and the key cracking，thus ensure data security and confidentiality. At last，a bus encryption simulation platform is built up and the results are presented to validate the proposed method feasible.