Seeking "third neighbor" is an important component in Mongolian multi-support balanced foreign policy since 1990s'. This paper discusses the specific meaning and background of "third neighbor" seeking diplomatic initiative of Mongolia, as well as practical effect and regional influence arising from this diplomatic initiative. This paper reached the following results about:The main purpose of Mongolia to find the "third neighbor" is, to offset the surrounding insecurity caused by two neighbors, China and Russia, and to enhance its own international status and influence. Indeed, in this context that Mongolia has achieved certain results, but, it also makes Mongolia involved itself into the "Vortex" of post-Cold War great power rivalry in this region, thus demonstrating that the risk and vulnerability of this diplomatic initiative.