This paper proposes a conceptual framework to analyze firm's participation strategy on national R&D projects, and examines their strategic behavior under the different types of environment. It identifies four dimensions of participation strategy and four types of participation strategy associated with two environmental variables : the speed of technology change and market competition. Several hypotheses are developed. They represent how firm's participation strategy varies according to the different types of environment. For empirical test, the selected 643 national R&D projects are surveyed by the structured questionnaire. Data are collected from 219 respondents. The empirical test shows that hypotheses are supported. Finally, this study discusses its implication and the area of further research.