Abstract: To reveal the relationship between optimizing a certain function of the system and optimizing the relevant functions of its subsystems,which are necessary for realizing the function of the system,this paper studies the mechanism by which the function of the system is not equal to the sum of the relevant functions of its subsystems after probing into system function additivity,and obtains some laws about optimizing the system and its subsystems on condition that their functions are addible.Thus i...

Key words: system； subsystem； system function additivity； system function optimizing；