This paper aims to investigate how tensification preference has changed over time and discuss how appropriately tensification preference is reflected in Principles of Standard Pronunciation and Standard Korean Language Dictionary. For this research, a questionnaire survey of tensification preference was conducted. 173 test words were used and 156 native Seoul speakers participated in this survey. The results have shown that tensification preference has gradually increased from older to younger generations. In addition, Principles of Standard Pronunciation and Standard Korean Language Dictionary do not reflect real pronunciation appropriately. Therefore, some ways of incorporating the actual pronunciation of Seoul speakers in the Principles of Standard Pronunciation and the Standard Korean Language Dictionary are suggested.