This study investigates the comparative of family firm and nonfamily firm’s performance attributable to international diversification in Taiwan, and added economic factors to test our research. We use agency theory to investigate the motivation of international diversification and the impact of firm’s agency problem on the extent of firm diversification and the performance attributable to diversification. If family firm’s alignment effect dominate entrenchment effect, family firm’s performance attributable to diversification will better than nonfamily firm. On the contrary, If family firm’s entrenchment effect dominate to alignment effect , nonfamily firm’s performance attributable to diversification will better than family firm. The empirical results in our research show that family firm’s performance attributable to diversification is better than nonfamily firm.