Development of oil and gas wells becomes more challenging due to high pressure, high temperature HPHT and sour service environment. At the current status, industries have commercialized sour service materials with up to 125ksi SMYS for mildly sour service. To realize 140ksi SMYS materials with SSC resistance at ambient temperatures, it should be needed to balance mechanical properties and corrosion resistance. In order to achieve 140ksi SMYS strength and corrosion resistance in a mildly sour environment (0.01bar H2S, pH=3.5), authors modify and adjust the amount of elements improving SSC resistance, such as chromium and molybdenum. SSC tests per NACE TM0177 Method A proved superior corrosion resistance under 90% actual YS. Furthermore, limitation in partial pressure of H2S and pH was also examined and this material is acceptable for the part of SSC region 2 in accordance with NACE MR0175/ISO 15156-2 at ambient temperatures.