Threshold ring signature enables any group of t entities spontaneously conscripting arbitrary n-t entities to generate a publicly verifiable t-out-of-n threshold signature on behalf of the whole group of the n entities, while the actual signers remain anonymous. In this paper, based on the ring signature scheme proposed by Hovav Shacham and Brent Waters in PKC 2007, we construct an ID-based threshold ring signature scheme, which has provable security under the standard model, and its security fits with the strongest security definition of ring signature proposed by Bender, Katz, and Morselli in TCC 2006. Besides, our scheme is very efficient.