After becoming North Korea's leader, Kim Jongen conducted nuclear tests and missile launches, which not only deepened the relevant countries’ concern about the security situation in the Korean peninsula, but also caused the South Korea to introduce THAAD system from the US, causing a series of knock-on effects. After going through Park Geunhae government’s “Choi Sunsil scandal”, Moon Jaein became the new president of South Korea. As North Korea walked to more extreme on the nuclear issue, Moon government, which originally wants to inherit and carry forward the "Sunshine Policy", has gradually changed security strategic diplomatic stance by not only strengthening the "traditional" alliance with the United States, but also by discussing necessity of enhancing Korea-US and US-Japan alliance. However Moon government knew the “violence to violence” method might help improve the military deterrence against North Korea, but it’s not conductive to ease the situation. This paper adopted literature research method to analyze the influence of South Korea security diplomacy’s strategic change and its influence on the Korean Peninsula. South Korea realized that strengthening military alliance is not a rational choice, but insisting conversation and peace negotiation can find the way out of the dilemma. By doing this, South Korea performed a “sports diplomacy” to North Korea and brought Korea peninsula back to a relatively peaceful and consultative atmosphere.