This study investigates the effect of locus of control on the relationships among product innovation, management accounting system (MAS), and organizational performance. 300 participants were randomly drowned from the electronic industries¡¦ managers in Taiwan Security Exchange and 132 useful responses were used to validate the hypotheses by path analysis. The results shows that: 1. Product innovation and organizational performance have a significant positive relationship 2. Product innovation and perceived usefulness of MAS information have a significant positive relationship 3. Perceived usefulness of MAS information and organizational performance are positively correlated 4. Product innovation has an indirect effect on organizational performance through perceived usefulness of MAS information 5. When managers tend to be internal locus of control, the linkage between product innovation and perceived usefulness of MAS information will be stronger 6.When managers tend to be internal locus of control, the linkage between perceived usefulness of MAS information and organizational performance will be stronger. However, when manager tend to be external locus of control, the hypothesis between perceived usefulness of MAS information and organizational performance is not supported. Management implications of this study are suggested. Businesses facing the global competition have to adopt the strategies of product innovation to create profits, promote market shares and improve strength of competition and then achieve organizational performance. Business using higher degree of MAS information will improve their adopting strategy of product innovation and enhance their organizational performance. Managers with internal locus of control will aggressively use MAS information and improve the linkage between product innovation and organizational performance effectively.