This study had two main purposes. The first was to clarify the relationship between structure of interaction and stability of romantic relationships, and the second was to compare the effect of the total intimacy level of a couple with the individual levels of intimacy using a pairwise correlation analysis in order to determine a couple's interdependency. Questionnaires were completed by 59 couples (college students in romantic relationships). The feature of interaction structure was measured by the frequency, strength, and diversity of interactions, while the stability of a relationship was measured by satisfaction, commitment, and prospects of a continued relationship. The pairwise correlation analysis separated the correlation of the couple level from the individual level. The results indicated that the stability of relationships was affected by the degree of diversity of interaction at the couple level, and by the strength of interaction at the individual level. Finally, we discussed the function of relationship stability, showing the degree of diversity and strength of interaction.