A computer system and a method for tracking information flow are provided. The computer system divides an information flow tracking task into two decoupled tasks executed by two procedures. The first procedure emulates execution of instructions and divides the instructions into code blocks according to an instruction executing sequence. The first procedure translates the instructions of the code blocks into information flow codes and transmits them to the second procedure. The first procedure further translates the instructions into dynamic emulation instructions and executes the dynamic emulation instructions to generate addressing results of the dynamic addressing instructions. The second procedure executes the information flow codes according to the addressing results to emulate the instructions of the code blocks. Moreover, the method also tries to reduce the amount of data transmission between the two procedures when the first procedure executes the emulation task. Therefore, the efficiency of tracking information flow is enhanced.