This study examines the relationship between mental workload and the cognitive control implemented in multitasking activity. A MATB-II experiment was conducted to simulate different conditions of multitasking demand, and to collect the behavioral and physiological activities of 17 participants. The results show that implementation of different modes of cognitive control can be detected with physiological indicators, and that cognitive control could be seen as a moderator of the effect of mental stress (task demand) upon mental strain (physiological responses).