The multi-signature is a special signature which is generated by multiple group members with the knowledge of multiple private keys, while the subliminal channel is a covert communication channel that can be used to send a secret message to an authorized receiver but the message cannot be discovered by any unauthorized receiver. A (t, n) threshold scheme allows a secret to be shared among n users so that only t or more users can cooperatively reconstruct the secret. All multi-signature schemes available are for either Discrete-Logarithm-Type (DL-type) keys only or RSA-type keys only. In this paper, we propose a multi-signature scheme, which allows mixture use of DL and RSA-type keys and is suitable for the Ad-Hoc environments. Then based on the proposed multi-signature scheme, we propose a anonymous threshold subliminal channel scheme, in which the subliminal message sender is indistinguishable and the subliminal message cannot be derived without the cooperation of t or more users in the group, where t is a threshold value.