Due to the complexity and dynamic behavior in virtual environment, the efficiency is low when adopting traditional methods to prove the secure state of virtual machines. Ring signature has high computational efficiency and strong anonymity, so the the key management can be solved by using the certificateless public key system. A trustworthiness attestation scheme which adopted certificateless ring signature scheme in Virtual Machine (VM) was put forward. After the trusted physical environment of virtual platform was validated by the Private Key Generator (PKG), the virtual Trusted Platform Module (vTPM) signature key was generated by PKG and vTPM manager using certificateless signature algorithm, and the ring signature was employed by VM to perform remote attestation and hide attestor's identity in ring members, which realized the attestation of VM's anonymous identity and state. After completion of the proof preparation, the VM does not need to generate virtual Attestation Identity Key (vAIK) certificates repeatedly in the process of attestation and migration, thus greatly improving the efficiency of attestation. Consequently, the proposed scheme has strong security and anonymity, and it is suitable for the cloud computing environment with huge numbers of VMs.