Unconditionally　secure　signature　is　an　important　part　of　quantum　cryptography.　Usually,　a　signature　scheme　only　provides　an　environment　for　a　single　signer.　Nevertheless,　in　real　applications,　many　signers　may　collaboratively　send　a　message　to　the　verifier　and　convince　the　verifier　that　the　message　is　actually　transmitted　by　them.　In　this　paper,　we　give　a　scalable　arbitrated　signature　protocol　of　classical　messages　with　multi-signers.　Its　security　is　analyzed　and　proved　to　be　secure　even　with　a　compromised　arbitrator.