Purpose: This paper examines risk factors which affect project success, and proposes a method utilizing the average potential satisfaction index(API) to evaluate how much the satisfaction level of the personnel involved in the project can change by reducing the risk. Methods: The current study derives 11 risk factors affecting project success from literature review and conducts survey of 253 subjects who have project work experience. A modified Kano`s questionnaire using 5-point Likert-scale is applied to investigate the amount of satisfaction or dissatisfaction when the risk factors are reducted or not, respectively. Results: The respondents consider that the risk factors which include the three elements of project management( schedule, quality, cost) is more important than other risk factors related to the project environment, and technology and profitability. Conclusion: The average potential satisfaction index proposed in this study can measure the perception on the risk factors of the personnel involved in the project, since it has a strong correlation with the perceived importance by the respondents in this study.