The article stems from the agency theory and research on ownership and representatives in Vietnam state-owned enterprises to analyze the effects of separating ownership and management power on the business performance of stateowned coopeartions and groups. By researching some typical group models in Vietnam, examining and evaluating the position, role and interfere mechanism of the state entities in state-owned groups, the author concludes that: it is the lack of apparent separation between ownership and management in state-owned economic groups that enables managers to pursue their personal goals, which results in unsound decisions that may seriously affect the state investment capital.